This helped me a lot when I had trouble sleeping. I kept a pencil/paper by the bed. I found I didn't need to turn on a light or anything. Just the reach over and write the thought in the dark. I'd wake up in the morning and find I had a paper covered in illegible scribbles, but for some reason it worked.

Also sometimes I still wake up early with thoughts of stuff I have to do. The trick for me to get back to sleep is to have somewhere for my mind to go. Concentrating on imaging lying on a beach somewhere can divert my mind and get it back to a sleepy place.