I don't know. When I'm awake, I tend to be a little more hesitant, and I think about what I do. When I'm goddamn exhausted, then I just react to whatever's happening in the game. Maybe if I did everything based on gut instinct then I'd play better.
Anyhow, I can't tell if I'm better, or worse, or the same when I'm gaming when I'm tired. Depends how tired though. When it gets to the point where all I've got is the most fundamental of motor functions, that is, clicking the mouse, I guess it becomes problematic.
