Tell us about yourself!
We do this by putting a mixing bowl out during a snowstorm. That way we know the snow is fresh and undisturbed. Then we just mix in one can of sweetened condensed milk.
Many people have separate hot and cold valves. This way you can adjust the water temperature to what you want and then shut off just the shower head.Alternatively, you could install a single lever handle valve, but as the post says that would be much more expensive. And you couldn't install one in a rental situation, where you could do this fix.
OR, you could write a love note to your wife. You don't HAVE to be evil.