I have begun using a technique to fall asleep and it works miraculously well. I start with my toes. I think about them, from the outside, from the inside. Then I work my way up my feet, my legs, doing the same at every pause. As I do this often one of my legs begins to spasm. It starts in my knee and it tenses up momentarily and then let's go again. I find it works best to just go with it. It's doesn't hurt and it doesn't last long.