I hate sleepless nights... They don't happen to me too often anymore now that I'm not working in sales call centers lol I used to wake up with stomach cramps and acid reflux, dreading going to work. I'd dream of making sales calls for the hour or 2 I'd actually get "real" sleep, and then wake up and have to go make more sales calls!
That sounds awful. Though in some ways, its not as bad when I know why I'm awake. Then there's a chance of doing something about it. It's the nights when there's no reason, you just don't tip over the edge into sleep...