when i was a kid i had a lot of nervous energy. i was always shaking my leg, or pacing, or tapping, or doing that thing where you roll a pen back and forth over your knuckles (when i got older and finally learned how to do it in chemistry class).
they* like to say nervous habits are the product of sexual frustration. for the record, whether or not the well has been dry, i've always peeled the labels off my beer. off topic.
it isn't the kind of thing people remember details about, so i don't know when i stopped, but let's say at some point between ages 17 and 19, i just cut it out. i've no inkling why. i just know i gradually came to realize in college that i didn't really do those things anymore and didn't really have the urge to.
i also don't know when it started again and i don't know why. but i shake like the dickens these days. and i'm constantly reminded of it because of a little coin bank on my desk here that jingles every time i shake my right leg. it drives me absolutely crazy.
* for the most part, i've found that the kind of people who'll cheerfully remind you of such hogwash tend to be more sexually frustrated on average than the people who won't. and strangely, they all like to say it as if it's deadly serious (and recently proven) scientific fact, as if you've never heard it before and you're supposed to be impressed and thank them for their insight into your psyche. seriously. hurt yourself.