From That Hideous Strength by C. S. Lewis:
Suddenly…desire (salt, black, ravenous, unanswerable desire) took him by the throat.
…[This desire] disenchants the universe. Everything else that Mark had ever felt – love, ambition, hunger, lust itself – appeared to have been mere milk and water, toys for children, not worth one throb of the nerves…
…It is idle to point out to the perverted man the horror of his perversion: while the fierce fit is on, that horror is the very spice of his craving. It is ugliness itself that becomes, in the end, the goal of his lechery; beauty has long since grown too weak a stimulant.