I agree with reading a book when you can't sleep. It can help get your mind off things if you can't sleep because you are thinking too much. Redirecting your thoughts through meditation can be helpful as well.
You can also take a melatonin supplement. Melatonin is the hormone your brain produces at night to help you go to sleep. If your sleep hormones are thrown off, it' can be difficult to feel like it's time for sleep.