I never used to be able to sleep on my back; it was just too distracting to have my eyes facing anything other than a pillow or a wall. That habit changed after i broke my collarbone, since i couldn’t find a way to get onto my stomache, and sleeping on my side just ground two pieces of freshly broken bone together. As a result, i learned to sleep on my back. I think my learning was enhanced by the fact that i am usually dead tired by the time i get to the bed. In the past i used to be one to stay up for hours, tossing and turning, but these days i seem to have designated the bed as being used just for sleeping and my sleep process goes much more smoothly that way.