Some time ago, we featured an article on the acceptable, good, and perfect will of God. Looking at passages from the Scriptures, some of the Fathers and the life of St. Galgano, we endeavored to explain that there are varying degrees of holiness a Christian is capable of obtaining. One degree is merely doing what is acceptable to God; i.e., not sinful. This may allow one to eek one's way into heaven, but it does not constitute holiness in the strict sense. Another degree is doing the good, that is, orienting our life around God and making a sincere effort to be a good Catholic. Then there is the third degree, the way of perfection, which consists in denying attachments to this world in a heroic degree to attain sanctity above all else. Those who make progress in this way of perfection are saints in the most perfect sense of the word.
This concept of three stages is well-attested in tradition, whether speaking of the three conversions in the spiritual life as does Fr. Garrigou-Lagrange in his classic book by the same name, or the three-fold path of Purgative, Illuminitive and Unitive, or the patristic idea of three levels of "reward" granted to confessors, virgins and martyrs. There are differences between these variant concepts, of course, but the idea of a three-fold progression in holiness is firmly rooted in Tradition.
Whichever schema we choose, the fundamental movement is preferring the good to the evil, then preferring the better to the good, and finally the best to the better. A person who has attained a high degree of sanctity understands the variations along this spectrum and always calls those seeking perfection to abandon all, even the good, for the sake of what is best. The saints are all different, but the one characteristic they share is abandonment. This abandonment may look strange or harsh to those on the outside, almost as if they are denigrating things that are in themselves good - like a stable career, spousal love, a good reputation, etc. - but in fact, they recognize that the good can become the greatest obstacle to the best.
A classic example of this principle in practice comes from the life of St. Elizabeth Ann Seton (1775-1821). Mother Seton was a loving, tender woman - but she also was ardently devoted to God as her ultimate end and had a sound Catholic sense of the hierarchy of goods. St. Elizabeth Ann Seton was a very careful guard over the spiritual lives of those entrusted to her care. If she saw a sister who did not go up to communion, she often inquired as to why. Once, a sister who did not go up to communion revealed to St. Elizabeth that she had not been feeling well and was a bit fatigued and so could not keep the Eucharistic fast.
"Mother," the sister said, "I felt a little weak, and took a cup of coffee before Mass."
"As, my dear child," said Mother Seton sternly, "how could you sell your God for a miserable cup of coffee?" 
Coffee, of course, is not intrinsically evil. Nor is there any mandate to receive communion every morning, not today, much less the early 19th century when frequent communions were less common. Furthermore, the sister stated that she was feeling weak, perhaps a tad sick. So she was certainly not in any sense morally 'wrong' for taking a drink of coffee before Mass. Yet still, the seemingly harsh words of Mother Seton, "How could you sell your God for a miserable cup of coffee?"
Of course Mother Seton's admonishment is one of love, not of mere nitpicking. St. Elizabeth had a keen understanding of the hierarchy of goods; there is a spectrum of good, better, best, and that for those seeking perfection, the biggest enemy of the best is the good. Coffee is not bad; for many of us, it is an integral part of our daily routine. But when compared to God, it becomes a "miserable cup of coffee." Any worldly good becomes "miserable" when compared to the glory of God. A cup of coffee. Your career. Your apostolate. Even your family. "If any man come to me, and hate not his father, and mother, and wife, and children, and brethren, and sisters, yea and his own life also, he cannot be my disciple" (Luke 14:26).
Again, we are not talking about things that are morally bad, but in choosing to forego things that are good in order to obtain those spiritual riches, stored up "where neither moth nor rust consumes and where thieves do not break in and steal" (cf. Matt. 6:20). Are there goods in our own lives which, by the priority we give them, become "miserable" in that they keep us from achieving our highest in Him?
 Mrs. Seton, Joseph I. Dirvin, C.M. (Basilica of the National Shrine of St. Elizabeth Ann Seton, Emmitsburg, MD., 1993), 342