Cheerily exhausted

How do we tell I'm exhausted? I monologue my entire drive, in large part to keep my mind on the act of driving. I discuss with myself my surroundings, the internals of my brain, the strangeness of other drivers, my car, y'know. The everything that might be relevant. (I bet on the way home I sing my monologue instead) Also, apparently, random and strange accents/ways of speaking.

On the plus side? I'm evidently cheery and easily amused in my exhaustedness!