Whenever I feel like that, it makes me realize I need a vacation. And I feel like that a lot. So I'll take one day off work and be a happy hermit all day, and then I can go back to life a little bit more restored.
This often helps me, too.
No matter my intention, it seems I have a finite capacity for being around people - I mean, I'll have days and days where I manage to go to work, and at a certain point...I just need to stop. It makes me wonder what would happen if I never took "mental health days".
I think if I were to entirely withdraw from society, however, I'd most miss those odd, unexpected encounters: for example, I was out walking later at night (I live in a large-ish city), and some homeless guy started talking to me. I was beyond nervous, and not at all eager to talk to someone who could easily hurt me very badly, but it ended up being interesting and surprisingly comfortable (relative to my other social interactions). We walked together for several blocks while he was telling me about his circumstances. I learned about the life of another human being, in a very unconventional way. In a way, I guess, I sort of live for that kind of thing: rare, unvarnished, unexpected, beautiful connection with another human being.
At the same time, on most days, I just want to say "**** it" and retreat to my efficiency nest with books and films and music and Internet connection and knitting paraphernalia, and never talk to anyone except my dearest friend/sweetheart.