Sounds to me like you're an introvert. Doesn't make you anti-social, just someone who needs to recharge their energy alone; as opposed to extroverts, who get their energy recharged by being around people. (P.S.: I'm an introvert)

I'm normally very social, but I need down time pretty frequently. I think most people do, actually. Anything gets old after too long a stretch.

Yes, I can. I had to learn how to force myself to be social, but I think many people think I am good at it. I spend a lot of time reading, which most people don't see.