Hi Barbara,
I agree with what some of the others have said. I think you are overdoing it and then it is almost like you crash once you're off your feet. I am bad about doing to much at times and pay for it for a couple of days afterwards. I am having one of those days today where I can hardly hold my eyes open and feel completely drained. I am also amazed that you can stand for 8 hours! That must be tough. Try and rest as much as possible.
Kendra