Over the years I've heard many changing theories when it comes to health and science. Everything from the number of eggs that is safe to consume to ozone holes that appear and then disappear. One of thing that hasn't changed much is the standard recommendation to get 8 hours of sleep. Unfortunately, not everyone is able to get a solid eight hours of sleep for a variety of reasons.
Some people have a problem falling asleep and others wake up in the middle of the night and have a tough time getting back to sleep. If you've ever woken up at 2am in the morning and found yourself watching the clock as the hours pass by you know it can be frustrating. Trying to will yourself back to sleep is very difficult, especially if you have a busy mind.
A few years ago I read something that was bit of an eye opener to me. If you look back in history you would find that people used to sleep in 2 shifts. They would go to sleep sometime after dusk and sleep for a few hours. They would wake up after a few hours to do some chores, read, or whatever else they desired before going back to sleep.
So now if I have a hard time getting back to sleep within a half hour I just get up and do something constructive before going back to sleep. This way you rid yourself of the pressure of trying to get back to sleep and at least you've accomplished something.