Um...because by then, I guess, you're pretty tired, and some people (like me) never feel tired, even when they are. They don't realise it, and when you're tired, everything is awesome, or funny. Some people go totally crazy when they're tired. Others are super irritable. I'm usually a bit of both. To be honest, I have no idea, I'm just linking up some stuff I know.
well, they do say that if you've been awake for too long, say..hmm..14 hours, the brain usually tends to work slower because t's exhausted. i've actually heard that 15 hours almost equals having 1 promille alcohol in your blood, so one starts to act like they're high by then.
So the longer one stays awake, the more one usually loses focus. except for if you drink coffee or drink something with pretty high energy amount; then one starts acting really weird.
