...Please be nice to your Sales Assistants, they have to deal with a near unending parade of moronic dicks at this time of year, don't make it worse. It's not their fault you didn't do your Christmas shopping months ago like someone with some sense. They're at breaking point, you don't want to have to try and comfort some sixteen year old girl who you've just reduced to tears in the middle of the shop floor, do you?
So be nice. If only because when you're giving your credit card details to someone on minimum wage you probably don't want to piss them off too much.