Having to do the morning shift after doing the night shift the day before.
It's like, motherfucker, I came home at 10 o'clock at night (and that's only because I was lucky enough to get myself a ride - otherwise, it'd have been 11 o'clock), had about 2 hours to eat and do whatever before going to freaking bed around midnight. And now, at 8 AM, I have to wake up and go right back to work again.