A man determined to take revenge will change his mind in confession, but soon afterwards he will join his friends and enjoy speaking about his quarrel. He will say that but for the fear of God, he would have done this or that; that the divine law with regard to forgiveness is hard; that, God willing, taking revenge should be allowed.
Yes, it is quite clear that, though this man has given up sin, he is greatly burdened with attachment to sin. He is in fact out of Egypt, but in desire he is still there, longing for the garlic and onions which he enjoyed eating there.
He is like the woman who has put a stop to her love affairs, but still takes delight in being courted and surrounded by admirers. Alas! Such persons are certainly in great danger.
From Introduction to the Devout Life