You can't really stop it, but a hairdryer clears it off really fast! Only way to really stop it is cover it with a towel, just depending on the bathroom set up you have using clothes pins to secure a towel against the mirror will give you a clear mirror, or you can use a squeegee to clear it as well, I have a squeegee that I use to get all of the water off of the shower walls and out of the bathtub, I have used that same squeegee to clear the bathroom mirrors, but only because I am lazy about cleaning, and cheap, and I don't want to use too much window cleaner.