Anatomy of Temptation

First, you do what you want to do, even though you "know God's decree that those who practice such things deserve to die." and only then do you "give approval to those who practice them" (Rom. 1:32).  You start to see yourself as either special or as hopeless, and thus the normal boundaries don't seem to apply.

It might be that you are involved in certain patterns right now and that you would, if asked, be able to tell me exactly why these are morally and ethically wrong. It's not that you are deficient in cognitive ability to diagnose the situation.  It's instead that you slowly grow to believe that your situation is exceptional ("I am a god"), and thus you find all kinds of reasons why this technically isn't theft or envy or hatred or fornication or abuse of power or whatever ("I am able to discern good and evil"). Or you believe that you are powerless before what you want ("I am an animal") and therefore escape accountability ("I will not surely die"). You've forgotten who you are.

Tempted and Tried, Russell D. Moore, Crossway, 2011, pages 36-37.