Have you worked third shift before? They can take quite a toll on you, both mentally and physically, so it's really important to take care of yourself as best as possible. If you do, your job won't seem half as bad and you'll be in better shape.
I have before, but it's been a while. I like the shift and I was able to get my sleep schedule adjusted just fine. I think it's just the transition, being unemployed and at home most of the time for the past month means I got to spend a lot of extra time with my girlfriend. But now, working nights, it's as if I'm seeing her less that when I worked regular daytime hours.
I used to work one night shift a week and my boss would book my next day shift the day after I finished my night shift. So I worked Monday 7am, Tuesday 7am , Wednesday overnight and then Friday at 7 am. She somehow figured Thursday was a day off even though I was definitely working on it. I had a sort of routine where I would push myself to stay up late Tuesday so I at least slept in Wednesday and then on Thursday I would only sleep about 3 hours so that I could get to sleep at night for my Friday shift. The only worthwhile thing is we had this piano in the store and this man would come in almost every Wednesday night to play Mad World. He played other things, but that one was my favorite. Point being, schedule transitions totally suck.