I turn the water off.

Growing up we used to live in a house with what I swear was the smallest boiler ever so the hot water would only last for maybe 1-2 showers before needing some time to get hot again. So leaving the water running meant no hot water midway through the shower, or forcing the next person to wait to take a shower.

It's a habit that stuck with me ever since, I've found that I don't really need the water running the whole time anyway.