You gotta make like a safecracker.

If you want to get the water just the right temperature in the shower, you need to use the Safecracker Technique. This involves precise movements of the cold water knob. Imagine you are a safecracker. You're spinning the dial, clicking one tiny notch at a time. It's like that, except, instead of packets of crisp twenties, your goal is only a shower at the right temperature. One millimeter too far, and the shower's freezing. One millimeter too far in the other direction, and it's scalding. It really tests your patience and your fine motor control.