A good talk on the high level neuroscience ideas behind sleep. It lines up pretty well with my own experiences. Prior to graduating with my Phd from UIUC, I had a horrid completely random sleep pattern from which I would suffer (probably still suffer) neuro-psychological issues - things like listlessness, incoherent memories (still suffer from that), and maybe some levels of depression. Close to when I had to defend my thesis, I recognized I was in trouble and I had chanced upon a BBC documentary on sleep and the human circadian rhythm. In that documentary were some advice on how we can take steps to control light intake (among other things like caffeine intake) in order to restore some control to our circadian cycle. Took me two months or so, but it worked out and my sleep cycle has been "ok" since - waking naturally at 7am even without the aid of an alarm clock. On the whole, I feel much better now than I had before.