Something that has helped me fall back asleep during restless, sleepless nights is thinking of a story I want to write.
I think of the setting, characters, plot development, etc. I think of as many details as possible as I lie there in my bed. Before I know it, I have fallen back asleep. Perhaps this works because it got my mind off my worries or the fact that I was not sleeping.
We can use our journals to write down these ideas as well- and, who knows? We may have some great ideas there for some future stories to write. I often think when we are in that semiconscious state our minds are often more creative, more intuitive, and more spiritual.
Another thing I might do when I am in this semi-asleep, semi-awake state is tap into my dream world. Sometimes I can bring up dreams I had many years ago! When I do this, I enjoy the images and then fall back into a nice sleep.