Experience as a checkout operator

Working as a checkout operator is always overrated by most people. I have no idea why but at first as a customer before I work as a checkout operator I thought that the work is easy, just scan the items and chuck them into bags. Oh well, it was before. After I started working as a cashier about a month ago i started to realise that the work is actually harder than I thought. Why is it difficult? At first you have to be fast, this is boring because you're not going to get better payment even if you're so fast like a superman or the flash anyway. If you work too slow you'll most probably be fired. Oh well, I'm not slow just moderate cause I want to be moderate. Second, you need to be really patient because there are many type of people do their shopping at that place where I a working right now. There was one time, I was working at night and there was a guy who was wanted to buy his groceries and placed it on my counter. After I scanned the items and put them in the bags, it was time to pay for them. All of a sudden he said, "Oh sorry, I don't have enough cash at the moment. I forgot to bring my EFTPOS card" (something like BANKCARD or MEPS in Malaysia) He wanted me to void some items from the list ( I scanned before). I did and then after a while he asked me "where are all the items that i'm buying?" The idiot customer was looking for groceries that he was buying. Oh well, I said there in front of your eyes. Actually everything that he wanted before he asked me to remove them from the list (isn't that stupid?). And then he didn't want some of the unvoided items (which are still in the list and he still want some of them) . What I did was cancel the transaction (void transaction). Intending to do it again and just rescan the items that he wanted. 

Oh well, some people here are just stupid and cranky. I hate them so much.