I have insomnia. I managed to keep it in check for when college started. Had to wake up 8 hours earlier than I was used to waking (wtf, right?). So I slept little the days before, took over-the-counter sleep aid, etc. and managed to wake up on time perfectly fine. But for the normal night, like tonight, sleeping doesn't seem logical. Mainly because I always feel like my time could be used to do something more worthwhile. I don't like the idea of sleep. I always want to do things - no matter what it is. I'd rather clean the house than sleep, because it's productive.
So I think that's where my insomnia stems from. At least partially. I don't like the idea of spending a third of the entire day doing nothing except being practically unconscious when there's so much to be done in the world. Thus, my mind keeps my awake at night.