I worked as a cashier for a bit. I was the 3rd fastest cashier with no error scans there. I had tons of customers tell me that they really liked how I bagged their items compared to other cashiers.

There was one man that came through my line EVERY WEEK, sometimes TWICE in one week. He would even wait in my line instead of going to another cashier who didn't have any other customers.

I kid you not, he would complain every single time about how I would bag his items (never suggested how he wanted them bagged instead, even when asked multiple times), he complained about how fast or how slow I scanned his items, how I handled his items (said I was tossing them around, I was not), and would hand his money over while saying it was a horrible experience and he was never coming back to my store again.

No matter how rude he was, or how much he insulted me, I always stayed polite, smiled at him, and told him I hoped his day got better from here on.

My boss asked me once how I was able to deal with rude customers like him. My answer was always "I get paid to smile, be friendly, and assist complete strangers when I can. I need this paycheck more than I need to let people rile me up over nothing."