I would often wake up in the middle of the night and not be able to fall back to sleep. I'd toss & turn for hours, absolutely miserable. It was made worse by the fact that with every passing minute I'd agonize over another lost minute of sleep.

It was only when someone suggested to me that simply lying still and focusing on my breathing was better than tossing and turning and worrying about not sleeping. If I couldn't sleep I could at least do that. It made a huge difference and helped me fall back to sleep.