Listen, kid. This is what happens: Somebody-girl usually-got a free spirit, doesn't get on too good with her parents. These kids, they're like tied-down helium balloons. They strain against the string and strain against it, and then something happens, and that string gets cut, and they just fly away. And maybe you never see the balloon again. It lands in Canada or somethin', gets work at a restaurant, and before the balloon even notices, it's been pouring coffee in that same dinner to the same sad bastards for thirty years. Or maybe three or four years from now or three or four days from now, the prevailing winds take the balloon back home, because it needs money, or it sobered up, or it misses its kid brother. But listen, kid, that string gets cut all the time."
"Yeah, bu-"

"I'm not finished, kid. The thing about these balloons is that there are so goddamned many of them. The sky is choked full of them, rubbing up against one another as they float to here or from there, and every one of those damned balloons ends up on my desk, one way or another, and after awhile a man can get discouraged. Everywhere the balloons, and each of them with a mother and father, or God forbid both, and after a while, you can't even see'em individually. You look up at all the balloons in the sky and you can see all of the balloons, but you cannot see any one balloon.

John Green