Alcohol's novelty has worn off for me; drinking to avoid boredom doesn't work. When I find myself outside of the party mood and bored, I get tired, antisocial and alienated, and just want to get the fuck out. I didn't say any goodbyes last night; I was in far too foul a mood to go through the motions. I noticed that when I'm upset and in a social situation, I keep a resolutely neutral expression, forcibly making my facial muscles relax. If I look irritated about something, I'm probably in a better mood than when showing nothing at all.
Some people love floating from one person to another, making light conversation, or perhaps just watching people go about their merry business. I can't stand it - I like to get into heavy conversation, and most parties I go to just don't encourage that sort of thing. Last night was no exception. It was mostly a much younger crowd (I'd guess a median of about 22), and the conversations I heard there I'd heard or participated in far too many times previously.