Catherine of Siena is beautiful in the Office of Readings today:
The eternal Father, indescribably kind and tender, turned his eye to this soul and spoke to her thus:
‘O dearest daughter, I have determined to show my mercy and loving kindness to the world, and I choose to provide for mankind all that is good. But man, ignorant, turns into a death-giving thing what I gave in order to give him life. Not only ignorant, but cruel: cruel to himself. But still I go on providing. For this reason I want you to know: whatever I give to man, I do it out of my great providence.
That's the whole story of misery and sin; we twist the good gifts God has given us into a sort of violence towards ourselves, We grasp at what is freely given to all and try to hoard it for ourselves. We cling to miserable little consolations rather than risk opening ourselves up to the Consoler who is the Spouse of the soul.
The moral theology of the devil starts out with the principle: "Pleasure is sin." Then he goes on to work it the other way: "All sin is pleasure."
After that he points out that pleasure is practically unavoidable and that we have a natural tendency to do things that please us, from which he reasons that all our natural tendencies are evil and that our nature is evil in itself. And he leads us to the conclusion that no one can possibly avoid sin, since pleasure is inescapable.
After that, to make sure no one will try to escape or avoid sin, he adds that was unavoidable cannot be a sin. Then the whole concept of sin is thrown out the window as irrelevant, and people decide that there is nothing left but to live for pleasure, and in that way pleasures that are naturally good become evil by de-ordination and lives are thrown away in unhappiness and sin. (Thomas Merton, New Seeds of Contemplation, 93)