From what I see too many pilots overestimate their wakefulness at times, and underestimate their need for sleep prior to reporting for a night shift.
I have to get @6 hours minimum sleep during the day prior to night shift and I have stay awake/alert all night in order to function comfortably when the bell goes off. If I go to sleep during a shift it takes a long time to wake up, and that is usually half way to wherever, so I don't do it. I figure if I'm at work I stay awake and at least do something to keep me brain engaged.