That Verge of Sleep and Waking

I know when I lay down to go to bed, it's really the only time of the day that I have to focus completely and freely on whatever I need to think about without feeling guilty. I think a lot, but most of the time I'm supposed to be thinking about something else when I'm thinking about whatever I want, so lying in bed is my only free time. What do people think about when they lie down at night? Is it a somebody, or planning for the day tomorrow? Is it a worry or a smile that puts them to sleep at night? What do they think about on those nights where you can't even keep your eyes closed, you're so awake? I guess it's good we can't read minds, because I think those moments between lying down and sleeping would reveal a lot about a person.