Do you know what keeps me up at night? Believe it or not, it's not my worries, fears or frustrations. Many, many years ago, two reasonably wise men taught me the art of taking said worries, putting them in a box and archiving them somewhere in my brain. I've learned to only open that box when I absolutely need to. And, I call these men "reasonably" wise because I later learned that they weren't as successful at this task as their pupil.
No, it's not my worries, fears or frustrations, because when you box them up, it allows your brain the freedom to dwell on happy, creative thoughts. It's my brilliant ideas and creative energy that wake me up in the middle of the night. It's those "Aha!" moments that keep me from readily going back to sleep. I find myself focusing very hard on these thoughts so I won't forget them in the morning. Therefore, I've discovered it's best to just sketch them out or write them down immediately so I can clear my head and get back to sleep.
It's 4 in the morning and my mind has awakened me with thoughts of my new art student whom I'm to meet at 10:00 a.m.for our second lesson and I suddenly have all these inspired ideas of the path our lessons should take. So, I'm up making an outline. And I don't mind being momentarily awake while I jot down some notes or make a quick sketch. In fact, I already feel myself feeling sleepy again.
In short, don't allow your problems to clutter your brain and when you wake with an idea you don't want to forget, put it on paper and then go back to sleep.