CPX 98: The 6th and 9th Commandments
Catechism of Pope St. Pius X (CPX) p.123-124 Q/A 1-8
"Sometimes we are caught off guard by certain symptoms of pleasure immediately following a temptation. At most, this can only be a very slight venial sin. However, it becomes greater if, after we perceived the evil that has befallen us, we carelessly delay for some time and dally with the pleasure to decide whether we ought to allow or reject it. The sin becomes still greater, if, after becoming aware of the pleasure, we dwell on it for some time through downright negligence and without any determination to reject it. When we voluntarily and with full deliberation resolve to take pleasure in such delights, this deliberate purpose is of itself a grave sin if the object in which we take delight is also very evil."—St. Francis De Sales in "Introduction to the Devout Life," Chapter 4 part 6 on "How temptation and pleasure may become sinful."