I do both nights and days, because I do agency and I go where the needs are. When I started doing more nights, I get off and settles by 8am, usually wake up naturally at 12, do some chores if needed and nap from 3-6p. If I am off the next night, skip my nap to ensure that I sleep.
I have no problems staying awake or falling asleep usually. if I am completely exhausted, and cannot keep my eyes open, I just go to bathroom, set my phone alarm and take a 5-10 min snooze. Out of 8 years of nursing, I have done this mabey 5 times. It is enough to give the 2nd wind!! 3-5am are the worse times!!
Oh---another tip I learned was to put aluminum foil on your bedroom windows....it may be bright and sunny at 12noon and it is dark as night in my bedroom!!