I've noticed that when I sleep during the daytime (even if it's for as little as 5 minutes), later on that night I won't simply fall asleep normally. I'll begin to fall asleep aware of the entire gradual process, and eventually I'm placed into a lucid world. The entire process is enforced by accepting the sleep paralysis and just going with it, which is usually accompanied by this weird pressure-like sensation within my ears. However that dream state only lasts for a good of 3 or so minutes and then I wake back up, only to fall asleep again... this time normally.