You come to Las Vegas to play poker, to party, to do whatever you want to do. Whatever it may be, you always end up doing to excess and wearing yourself out. Extreme tiredness sets in and the only way to solve this is to go to bed and catch-up on sleep.
The problem is that when you try to sleep, you can't. You go into a half-sleep where you're sort of dreaming but still conscious of the real world. This state can last for hours before you finally drop off. This is bad preparation for what is to many, the biggest tournament of their lives.
A common problem that no one I've spoken to knows the name for.