My comings and goings tend to be off-putting sometimes; if I wander into a social group, but feel like I'm not really part of what's going on (due to lack of interest, not being part of the vibe, or whatever) I'll just leave with nary a word spoken. It's not that I'm annoyed or anything; I just feel that if I ain't participating, I needn't stick around. Unfortunately, I tend to act much the same way whether happy, sad, irritated, depressed, or pissed-off; it's not a real good cue as to my mood.
The kinda strange (I guess) thing about it is that when I'm doing it, it doesn't occur to me to act any other sort of way. I dunno if not acting like that is a learned behavior I never picked up, some 'natural' inborn instinct I lack, some weird psychological 'I don't deserve to be greeted and so won't do it myself', or what.