Stephen King. It (№ 215)

You can't just stop being a baby, immediately, with a loud crash, like the bursting of a balloon with the words "Burma-Shave" on the sides. Baby just goes out of you like air from a tire. And one day you look at yourself in the mirror, and from there on you looks an adult. You can continue to wear blue jeans, you can still go to concerts with Springsteen and Seeger, can be added hair, but the face remains the same - an adult.