Sometimes I just don't want to talk to people. I can be very anti-social when
(a) I'm having a bad day
(b) I'm struggling with a hard problem
(c) People are talking and having a good time and I'm trying to work and get stuff done

Interestingly, those three things are often related. Today at least two of them contributed, though there were also extenuating circumstances that brought out my introverted tendencies. But it got better in the last, oh, two hours. In that time I partook in some uplifting correspondence, shall we say, with my special someone. She's a dear, let me tell you.