Gene Cernan, Apollo 17 Commander
Just think about going to sleep on the moon inside of an oil can. And that's what we did. An oil can that buckled every time you pressurized it: boom-boom. And you're inside that oil can. You're on the surface of the moon, and it's time to rest or go to sleep, which is the biggest waste of time in the world—who wants to go to the moon to sleep? That's when you have a chance to think about these things. Think about what you just saw and where you are. Yeah, you think about those things. You don't think about them while you're picking up rocks and doing all these other things that you've got to do while you're there. But you think about them when you have a chance to stop.
(Photo: Having left Apollo's last footprints on the moon, Gene Cernan takes a breather inside the lunar module Challenger.)