I've trained myself to wake up halfway through my sleeping (at about 4am,) which is good because then I can remember more dreams, but there are times that I want to sleep 8 hours straight for a more restful sleep. I have a race coming up and I want to be completely rested for it. Without the aid of sleeping pills, what can I do to voluntarily switch between my 4,2,2 hour cycles and one long 8 hour sleep?