I think that one of the reasons that I act like this is that I hardly ever mentally relax. I just don't know how to do it. If I attempt to meditate, it's a focused and hard nothingness, not a soft one. This behavior may be due to my wholesome midwestern values that say "It's terribly rude to be hyper - nay, disgraceful! You should keep a tight rein on it at all times, no matter what." Sleepiness is one of the few things that makes it slack up a bit, that lets things flow instead of just stutter along.
One of these days I'll start posting things that don't involve me bitching about things or being critical, I swear. :)