"Do not imitate this world, but be transformed by the renovation of your minds, and you shall distinguish what is the good, acceptable and perfect will of God" (Rom. 12:12).
It is a teaching of the Catholic Faith that there are unequal degrees of beatitude in heaven. Session 6 of the Council of Florence taught that those in heaven "clearly behold the triune God as he is, yet one person more perfectly than another according to the difference of their merits."
This inequality of eternal beatitude is predicated upon the inequality in merit from soul to soul. Some souls fulfill the will of God in a nearly perfect manner, conforming themselves most intimately to Christ, and by doing so merit much glory; others, like the workers called at the end of the day in the parable of our Lord (cf. Matt. 20:1-16), are received into heaven, as it were, by the skin of their teeth. Each group will be saved, some close to perfect when they die, others only after enduring the purifying fires of Purgatory to various degrees.
Thus, heaven may receive those who toil ceaselessly for the Lord bearing the long hours and the heat of the day, as well as those who were only called in the last moment of their lives and many in between. There are different ways of fulfilling the will of God, more or less perfectly. There is a manner of fulfilling God's will that is perfect, another way that is less than perfect but still truly good and meritorious, and then a lesser way that is merely acceptable. While everybody strives to fulfill the will of God in the manner most consistent with his state and manner of life, and that "if the readiness is there, it is acceptable according to what a one has, not according to what he lacks" (2 Cor. 8:12), it is nevertheless true that certain forms of life and devotion are objectively better than others. This has long been understood in the case of virginity, for example, which the Catechism says is a "more intimate" way of following Christ, most appropriate for "pursuing the perfection of charity" .
In the passage from St. Paul cited above, the great Apostle speaks of a will of God that is good, acceptable and perfect; that is, a manner of following God that approaches evangelical perfection, a lesser way that is still "good" but not perfect, and finally a way that is merely "acceptable" or tolerable. This parallels with our Lord's teaching in the Gospel that whilst obeying the commandments of God (i.e. avoiding mortal sin) will secure eternal life, there is another, higher way to follow Christ for those "who want to be perfect" (Matt. 19:21) - the traditional evangelical counsels. Those who observe the evangelical counsels are living an objectively "better" life than those who do not.
The Church Fathers also admitted of different degrees of perfection based on one's manner of following God. A common text that lent credence to this idea was Mark 4:8 and Matthew 13:8, the parable of the sower, in which our Lord speaks of good seed, which "brought forth fruit that grew up, and increased and yielded, one thirty, another sixty, and another a hundred-fold" (Mark 4:8).
Following our Blessed Lord's interpretatiin of the parable with different sorts of believers, the Church Fathers had identified the different yields with different manners of life. The martyrs are those who produce a hundred-fold increase; the sixty-fold increase is assigned to the virgins, and the lowest yield, that of thirty-fold, is assigned to the faithful who remain in the married state. For example, St. Cyprian, when writing to consecrated virgins of the Carthaginian church, invokes the parable to remind them of the spiritual yield their state in life will produce: "The first fruit for the martyrs is a hundred-fold; the second is yours, sixty-fold" . The same parable is interpreted in exactly the same manner by Augustine (On Holy Virginity, 46), St. Jerome (Letter 68:2), and Origen (Exhortation to Martyrdom, 14).
While the idea of different levels of beatitude is well attested, the connection between this and different manners of living is not as well understood by contemporary Catholicism - even less the relation of the different ways of life to one another. Every Christian is to strive for perfection. St. Paul says in 1 Cor. 9:24 that we must run our race so as to win. The Christian life is often compared to an athletic competition by St. Paul. Note that in any athletic competition, although in the end the competitors will rank all along the spectrum from first to last place, every competitor subjectively is expected to give their all. If a runner does not strive to run as fast and as hard as he can, how can he be said to be running so as to win? Although not everybody will place the same, the essential characteristic of a competition is that one tries their very hardest. First place is the goal in every athlete's mind; if it were not, how could they be realistically running "so as to win"?
To relate this back to St. Paul's passage from Romans, we should all be striving to do God's "perfect" will, not just be content with what is merely "acceptable." In our own strength we could never hope to do this; but our Lord does not command what is impossible, and in grace such a life of perfection is truly possible. The saints are those who have attained it.
But such perfection is not possible in every state in life. This is why tradition tells us that martyrdom and consecrated virginity objectively merit a higher place in heaven than those living in the married state. There are various practices that Catholic tradition has hallowed as being sure means towards attaining holiness. St. Bernard and St. Alphonsus both compiled famous lists or "steps" that would lead to holiness; fasting, devotion to our Lady, Holy Hours, regular and devoted attendance at Mass, acts of penance and many other things also lead us towards holiness. All are forms of mortification.
But mortification, by its very nature, is difficult. It consists in nothing other than putting to death the deeds of the flesh, which is never easy. But it is necessary. This is why St. Paul says of himself, "I chastise my body, and bring it into subjection: lest perhaps, when I have preached to others, I myself should become a castaway" (1 Cor. 9:27); and he encourages this on every believer when he says, "For if you live according to the flesh, you shall die: but if by the Spirit you mortify the deeds of the flesh, you shall live" (Rom. 8:13) and "Mortify therefore your members which are upon the earth; fornication, uncleanness, lust, evil concupiscence, and covetousness, which is the service of idols" (Col. 3:5). Mortification is obligatory on every Christian.
The Christian who is perfectly mortified has attained perfection, because to be perfectly mortified means to be dead to this world and fully alive and set apart to God. Unfortunately, people are often led astray into thinking this perfection is available to them without too much effort. Popular Catholic books promise to help readers "unlock the power of the sacraments"; little pamphlets for Holy Hour devotions boast that they can quickly teach you "five ways to tap into the Eucharist"; books are published with collections of excerpts from the spiritual writings of the saints which are put forward as a "what-you-need-to-know" guide to Catholic spirituality; our spirituality, like our society, has become bourgeois.
These aids may be good to get one oriented in the right direction, but we fool ourselves if we think holiness is gained easily. The much-touted universal call to holiness means that holiness is possible for everybody, not just religious. But it does not mean that holiness is "easy" or that it is less rigorous to attain for the lay-person than the contemplative. There is no "lay version" of holiness that is effortless or can be reached with some self-help books in a few quick and easy steps.
There are different degrees of penance and different types of mortification, but all must do penance; all must be mortified. All things being equal, holiness is easier to attain in the religious life than the lay state. Yes, there will always be holy lay people and lax religious, and the former will be higher in heaven than the latter. But this is due to a defect in the observance of the religious; in other words, while a faithful lay person can attain a higher degree of holiness than a bad contemplative, a faithful contemplative will attain a higher degree of holiness than a faithful lay person, simply because the his manner of life is more conducive to mortification and holiness.
Does this offend you, dear reader? Does it upset you to think that some levels of holiness will not be open to you because of your state in life? It is true; Martha and Mary both do good, but Mary has chosen the better part. Certainly even us Marthas can cultivate a bit of Mary, but it is impossible that we should simultaneously receive the reward of Mary while living the life of a Martha.
There are always temptations to think that we can attain holiness without fundamentally mortifying our flesh or changing our manner of life. This is simply not the case. Yes, we may make great strides; we may move from what is merely acceptable to something better. But if we seek perfection - as we should - the way is always going to be difficult and will always involve great struggle. This is why common patristic symbols for the spiritual life all involve struggle: an athletic race, wrestling, a battle, climbing a mountain, etc.
There is a way to follow God that is merely acceptable, one that is better, and one that is perfect. A real path to holiness should involve moving from one to the next. A false path to holiness is one that will look to simply affirm what you are already doing, or that would seek to pretend that holiness can be attained without any serious effort. What is good for one may not be good for others; for a great sinner, merely getting him to stop blaspheming daily may be a considerable advance; but for a mature Christian seeking holiness, such a bar is set far too low. In that case, the good can become the enemy of the best.
In the story of St. Galgano, recently featured on our blog, the devil frequently tried to tempt Galgano by getting him to prefer the good to the best. After his conversion, Galgano felt strongly called to the eremitic life. His mother, happy that he was converted, nevertheless wanted him to live the life of a respectable, decent lay-person: God-fearing, devout, but also married and earning his way in the world. There is nothing wrong with that; many good Catholics live that sort of life. But Galgano was seeking perfection, and he was honest enough to understand it is not possible to attain perfection in a life-style that is merely "good." His mother's desire for him to live a life that was legitimately "good" became for him a stumbling block.
So he retreated to Mount Siepi to live as a hermit. But again he was tempted with a lesser good, this time to go back down and give all his goods to the poor before embarking about the eremitic life. Surely, making division of one's goods to the poor and organizing one's affairs before retreating into solitude is a good and wholesome thing to do? Certainly. But in Galgano's life it was a snare, as his vita tells us that the purpose of the devil's temptation was simply to get him to leave the mountain and return to the world, even if only temporarily, even if with good intentions. St. Galgano was seeking not the acceptable or good, but the perfect will of God, and hence once embarked upon his life of penance, refused to choose anything less than the way which was most perfect.
Where does that leave us, who are living in the lay state and cannot renounce all as the hermits did? Well, if you are still single, consider embracing the life of penance, as so many other saints did. But for those of us who are married, there is great grace in fulfilling our state in life; but let us not mistake the merely acceptable for the perfect. Let us ask ourselves, "What would my life look like if I were seeking to fulfill the perfect will of God? What would I look like as a saint?" We cannot imitate the great penances of the Desert Fathers in the lay state, but let us not deceive ourselves; there is room for much more penance than we practice. What does penance look like for a lay person?
Do we seek to fulfill our state in life perfectly, or only tolerably? Are we eager to latch on to mitigations, exceptions, and exemptions in our obligations, or do we make sacrifices by voluntarily renouncing these things as a means of challenging ourselves? Are the only times we fast on Good Friday and Ash Wednesday? Have we kept Advent penitential? Are we mortified in the use of our finances? How about in our sexual appetites? In what other ways do we "buffet our bodies to bring them into submission", as St. Paul says? Do we structure our daily routine around prayer and the service of God, or do we assume this is impossible and give God merely what is left over? If we were to really - I mean really - live our state in life faithfully and not just tolerably, what would it look like?
Again, we need not think that penance implies great austerities, but we are fooling ourselves if we think it does not require mortification. Let us reexamine our life. Are we deluding ourselves into thinking we are mortified when really we are living a manner of life that is merely 'acceptable' and not really 'good', much less 'perfect'? Remember, the biggest enemy of the best can be the good. We cannot imitate the religious life perfectly, but those who seek perfection, of whatever state, will approximate to the evangelical counsels as closely as they can. Society has changed, but the definition of holiness has not changed; neither has the steps to get there. St. Alphonsus' "Twelve Steps to Holiness and Salvation" applies equally to lay people as much as to religious.
One final quote from a saint who is not often associated with austere penances but who was exceptionally mortified: St. Elizabeth Ann Seton. Here is a prayer composed by St. Elizabeth as an act of abandonment to the divine will in all matters, even the most trivial:
"Considering the infirmity and corrupt nature which would overpower the spirit of grace, and the enormity of the offense to which the least indulgence of them would lead me - in the anguish of my soul, shuddering to offend my adored Lord, I have this day solemnly engaged that, through the strength of His Holy Spirit, I will not again expose [my] corrupt and infirm nature to the smallest temptation I can avoid; and, therefore...I will make a daily sacrifice of every wish, even the most innocent, lest they should betray me to deviation from the solemn and sacred vow I have now made." 
This is the prayer of a saint who sought perfection, not just what was "acceptable." The universal call to holiness means we are all capable, with great efforts done in grace, of attaining some degree of holiness; too often it is taken to mean that we are already basically holy. Instead of making the world holy, it has made holiness worldly. We ought to be exceptions to this. We know the path - and we know, based on the Church's tradition, that the path is objective; some things will lead us to holiness better than others, regardless of our intention. There is nothing wrong with watching a football game. But it is a holier thing to renounce watching football for the love of God than to read a book entitled Finding God in Football in order to convince yourself that your merely acceptable recreation is actually an act of piety. We know the acts of true piety, and the Church's tradition presumes they are objectively standardized and that those who do them in the right disposition will be holier than those who don't. Period.
Let us, then, follow the path that has been blazed for us, and begin by resolving to follow God's will perfectly in a spirit of humility and penitence. The way is not easy, but putting us souls under the discipline will render the yoke easy and the burden light. Let us have great confidence in our Lord to complete the good work He has begun in us (Php. 1:6) and remember that "I can do all things through Christ who strengthens me" (Php. 4:13).
Related: Dark Nights, True, False and Fashionable
Mass Marketing Mysticism
 CCC 916. See also St. John Paul II, Vita Consecrata no. 32, "“As a way of showing forth the Church's holiness, it is to be recognized that the consecrated life, which mirrors Christ's own way of life, has an objective superiority. Precisely for this reason, it is an especially rich manifestation of Gospel values and a more complete expression of the Church's purpose." More quotes from saints and popes on the superiority of the virginal state can be found here.
 Cyprian of Carthage, On the Dress of Virgins, 21
 Fr. Joseph Dirvin, CM., Mrs. Seton (Basilica of the National Seton Shrine: Emmitsburg, MD, 1993), 113