Moms of active preschoolers...how do you contain their energy?

My son is three and is a complete whirlwind from 6:30am until 9pm. He goes to preschool so there's activity there but it continues until we coerce him into bed. If there's quiet then he's getting into something (like on Monday when he was taking a bath, was able to reach the shower caddy over the shower head, get a hold of a razor and cut his lip with it all while I went to get his soap from the other bathroom). How do you maintain sanity?