customers

I work in fast food, I'm 21, and these customers really test my patience. I have to remind myself that I'm not allowed to curse at or hit the customers. Wondering how others in the same boat keep their cool with them. People always say my generation are rude and disrespectful but I've never had a customer my age give me any problems. They've always been patient but with some older folk is when things turn to hell when they order and after 2 minutes start bitching about where their food is like they were the first ones in.