How do you fix a misty bathroom mirror, when you want to shave?

My bathroom is so small, the mirror that i shave in is always always misty, this is driving me mad because the only thing that gets rid of it is opening a door, this is inconvenient as it would freak people out with the door open, or open a window, but then its freezing, anyone know an instant way to clear a misty mirror, OH ive also tried the cold water thing, doooowwnn work