I think I know what it is now. I've been forgetting to give myself "recharge-from-society" alone time, and now it's built up. So, I'm staying home for the third evening in a row, watching TV, playing video games and the piano, and I'm accepting it as normal-for-me, rather than feeling socially inadequate. I'm fine now -- just hadn't shut out the world enough, and it got to me. Maybe I should call myself Odo, from Star Trek: Deep Space Nine, because I need to return to my (socially) amorphous state every day or so in order to keep functioning. That trait of his is so metaphorical!