It's like an inverse proportion to how much sleep you missed the previous night. When you get 1/2x the usual amount of sleep one day, you make time to sleep for 2x hours the next night (where x is your usual amount of nightly rest). The real trouble comes on those strange days where you somehow forget to sleep at all. Then you're all 0/x and the inverse is undefined and who knows what the hell's gonna happen when that sleep debt kicks in? You may pass out in the middle of a meeting or you just might stay awake forever.

My point is... well, I don't have one. I'm kinda tired myself.