Just wanted to say that I've always wanted to take cold showers but never managed to pull it off because my body refuses to step into the cold shower stream. Somehow, until I read your post, it never occurred to me that I could start the shower at a nice warm temperature, step in, and then turn it down over the course of a few seconds. I've been doing this successfully for a few days and feeling great. Thanks!
BTW, I've found that changing the temperature of the water over time feels much less uncomfortable if the water is pouring directly onto my head than if it's going (say) on my feet.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.