I normally don't either, but there's been a few time.
it's weird. Anyone who doesn't get enough sleep is grouchy dear, it's normal (ok ok, everyone except the insanely happy-about-everything people) I've been known to doze in classes; though at my school the teachers either throw something (like a foam football or whatever) at your head, slam books on the ground next to your desk, or sometimes even dump you out of the desk so it never amounts to anything
I think that's a common problem for insomniacs. :/ some days I think being an insomniac means your brain never wants to go into the normal "sleep" mode most everyone else has. But eh, I'm not a professional so idk