My finger are retaining water.. how do I prevent it?

I'm going to go get my ring resized today cause it was a present and it's too big. Usually it just slips off my finger constantly! (super super annoying) But today of all days my fingers are retaining water the ring is still too big but it doesn't slip off as easy and I want it to be the right size. So how do I get my fingers to not retain water?