I've developed a bad habit: air conducting. It's like air guitar, where you play an imaginary guitar, except I'm conducting an imaginary symphony. I used to drum my fingers a lot, and I guess at some point I transitioned to the less annoying but more ridiculous air conducting.
Just now I picked up my Diet Coke (probably #7 for the day so far) with my right hand, and started conducting with my left hand without even initially realizing it.
Oh well. I guess that there are far worse habits to develop.
The sad part is that I don't even do it correctly. [Warning: the rest of this post is probably more boring than the first part.] I have a perfectly salvageable sense of rhythm; it's just the motions that I manage to screw up. A typical pattern is DOWN, right, left, up, DOWN, right, left, up. The important part is cutting down on the first beat, aptly named the "downbeat." Often I'll do something like DOWN, right, left, right, oh crap, DOWN, but the oh crap takes about half a beat, so suddenly I'm half a beat off, and my brain automatically rounds up to the next beat, and then I stop because I realize I just moved my hand down on the wrong beat. That's usually when I realize in the first place that I screwed up; the rest is fairly subconscious.
My #1 choice of instrument in elementary school was the drums, but the school didn't allow kids to learn the drums or guitar, those being the really popular ones. So, my next choice was the cello, which is a pretty difficult instrument to play properly. I decided that I had better things to do with my time and my parents' extremely limited funds than practice the cello all the time, especially being already quite aware that I had the coordination and finesse of some sort of mythical rock-beast. So, I decided not to learn an instrument at all. I think that was after I had already left the sorta-semi-pro choir I was in (the kind of choir that has performances that people not related to the kids in the choir would actually pay money to hear) after deciding that it also took too much time. I still remember what I learned, though, even though I can't really sing anymore: don't pronounce the letter "R" in the middle of a word, exaggerate "T" sounds and their kin, and always elongate vowel sounds and not consonants. "Gloria in excelsis deo" becomes "Glo-o-o-o-o-o-o-o-o-o-o-hia in exSHELseees d-aa-aa-ay-o." It sounds pretty silly if you're not in a big choir.