You will become acutely aware of how many people do construction or yard work just as you're about to fall asleep. The first time I did graveyard the manager for my department mentioned he'd just read a study showing that every 5 years of night shift takes 6 months off of your life. Some people seem to manage fine but I always spent like a full day sleeping at the end of the work week just trying to catch up and have never eaten more fast food in my life, even with a physically intensive job I was still gaining weight.