What does it mean to be “attached” to sin?
It means not fully giving up sin; not detecting sin enough to distance ourselves from it and every occasion surrounding it. It can also mean entangling ourselves in sin to the point where it becomes practically difficult to let go of sin, its occasions or to discard everything acquired sinfully. An example of such entanglement is cohabiting with an illicit sexual partner or building a business empire with stolen wealth.
St Francis de Sale discusses purifying the soul of affection to sin using a brilliant analogy of the Israelites fleeing from Egypt:
“ALL the children of Israel went forth from the land of Egypt, but not all went forth heartily, and so, when wandering in the desert, some of them sighed after the leeks and onions,—the fleshpots of Egypt. Even so there are penitents who forsake sin, yet without forsaking their sinful affections; that is to say, they intend to sin no more, but it goes sorely against them to abstain from the pleasures of sin;—they formally renounce and forsake sinful acts, but they turn back many a fond lingering look to what they have left, like Lot’s wife as she fled from Sodom. They are like a sick man who abstains from eating melon when the doctor says it would kill him, but who all the while longs for it, talks about it, bargains when he may have it, would at least like just to sniff the perfume, and thinks those who are free to eat of it very fortunate. And so these weak cowardly penitents abstain awhile from sin, but reluctantly;—they would fain be able to sin without incurring damnation;—they talk with a lingering taste of their sinful deeds, and envy those who are yet indulging in the like.
Thus a man who has meditated some revenge gives it up in confession, but soon after he is to be found talking about the quarrel, averring that but for the fear of God he would do this or that; complaining that it is hard to keep the Divine rule of forgiveness; would to God it were lawful to avenge one’s self! Who can fail to see that even if this poor man is not actually committing sin, he is altogether bound with the affections thereof, and although he may have come out of Egypt, he yet hungers after it, and longs for the leeks and onions he was wont to feed upon there! It is the same with the woman who, though she has given up her life of sin, yet takes delight in being sought after and admired. Alas! of a truth, all such are in great peril”.
– St Francis de Sales, Introduction to the Devout Life Chapter VII. The Second Purification, from all Sinful Affections.