Stress
There's lots of stress to this job, so much so that some days you might think stress is your job. Between fussy guests, temperamental chefs, lackluster benefits, whiny children, and sassy teenagers, and an at-times borderline chaotic work environment, you can expect to feel that you're on the go and never stopping for most of your shift.
You've also got to deal with irregular hours. You're only a nine-to-fiver if your restaurant actually has a nine-to-five shift and you get assigned to it. More likely, you're a four-to-midnighter, or a 5:00AM-opener, or an until-2:00AM-closer—or maybe you're even pulling a double.
There may be some consistency, but you're just as likely to find yourself working a variety of shifts throughout your week. The words "regular sleep cycle" will mean nothing to you.
Long hours working at times when everyone else you know is home enjoying themselves (like all those family gatherings and important holidays) can add to your general stress level, as you're constantly trying to explain that you have to work and can't make it. Oh well, at least you'll be able to help some other family celebrate Thanksgiving. Maybe they'll even let you try the cranberry sauce?
Just kidding, you've got a whole vat you can try in the back.