Derek leans into the petting, letting the touch sooth him a little. "I know. It's just that -- "

He takes a deep breath and exhales slowly, not quite meeting Stiles' eyes. "When I was your age, maybe a little younger, I thought I was in love with someone. And she hurt me. She used me to get to my family, so she could hurt them, too.

I know I'd never hurt you like that, but right now? My life is a mess. I mean, a huge fucking mess. And I don't want you getting hurt by my mistakes."