Cordelia: You want I should distract him? Make with the nice-nice while you slip by?
Angel: Don't be stupid. I'm that guy and the most beautiful woman I've ever seen is making eyes at me? It's either a bachelor party or a scam.
Cordelia: What did you just call me?
Angel: I'm sorry. You're not stupid.
Cordelia: No, after that.
Angel: I saw their production of "Giselle" in 1890. I wept like a baby, and I was evil!
Heartthrob - S3-E1
Wesley: It's sad. The only way some people can find a purpose in life is by becoming obsessed with demons. By the way, Gunn, technically that wasn't a Lurite, it was a Murite, a subspecies of the Lurite. The male sports a small telltale fin just behind the third shoulder.
Gunn: I'm so glad to know we're not the sad people obsessed with demons.
Answer: Due to his epiphany, Angel basically had the 'true darkness' he worked so hard to reattain ripped away from him, like his soul was after sleeping with Buffy.