It's been found that the natural nocturnal pattern for humans is to sleep for four to five hours, wake for an hour or two, then sleep for another three to four. The eight hour pattern is something imposed on us by artificial light and the industrial revolution. Now when I wake up at two or three, I putter around for an hour or two and go back to sleep until seven or so, then wake up alert and rested. Doing something useful with those late night waking hours is a lot better than being overwhelmed with anxiety about not being asleep for a solid eight hours.