"Brownslave".......do you personally WANT to work Saturday? Or are you working because you are being so called FORCED to work??
I mean if you don't want to and you say you are working because customers ordered stuff late, which is the case every single year. Why do you take it upon yourself to trash your Saturday and play the hero for other peoples tardiness?
Take the day off......enjoy yourself......and let them sweat it.....not your fault.
As my old union steward told me when I was a rookie many many years ago......"Don't sweat the petty things, but pet the sweaty things".
Think about yourself for a change......there's nothing wrong with that.