Ever Have One of Those Nights?

Did you ever have one of those nights when you just couldn't sleep?  Well, here I am; it's 3:40 am and I'm wide awake.  It's so quiet in the house and outside.  The only sound is the clicking of my computer keys.  I'm supposed to be at work in 5 hours (yawn).  Instead, I'm staring at my computer screen wondering why I can't sleep.