I thought of about a dozen really attractive women that I wouldn't mind having sex with, and then I realized, I'd probably be way too intimidated to actually perform adequately. I mean, I'm not inexperienced, but I'd be lying if I said I wouldn't feel ridiculously nervous having sex with somebody like Emma Stone; although she seems like she'd be really fun to hang out with. I have decent self confidence, I just don't have a lot of sex with random people. It's usually with girlfriends, friends that I'm interested in, etc. People I have at least some sort of connection and familiarity with. Never had a one night stand, been set up, or anything like that. If I got to hang out with Emma Stone, I'd probably just want to hang out with Emma Stone.
TL;DR - Karen Gillan