This is the most difficult part of the night for me. I ofter wake up after four or so hours and then can't get back to sleep. First, we have to try to get people to sleep all night long, so we don't have to talk about trying to get people back to sleep. The best thing to do is to not stay in bed and toss and turn and worry about not falling back to sleep, because it only makes things worse. Get out of bed, keep the lights low, and do something soporific, like, read a book, and within 30 to 40 minutes you will feel sleepy once again.
Some people call themselves larks, because their best hours are early in the morning.
This is a learned condition, not a genetically linked one, and can be changed within three to four weeks if you are motivated to do so. Larks should expose themselves to bright light, which is full-spectrum, late in the day or during the evening. Owls who wish to become morning people should expose themselves to sunlight early in the morning. This will help change your biological clock and put you in synch with your new time schedule. Some people remain awake 72 hours without dozing.