Annoying scales - why do they do this?

Hi all,



Does anyone know how I can eat sensibly for ages and have the scales tell me I'm the same weight, then one day tell me I've lost a few pounds, then be back to the same weight the very next day?



It's so frustrating that I wait for ages to see results, to think I've got them, only for scales to say I'm back to square one the next day.