My optimism and confidence come not from feeling I'm luckier than other mortals, and they sure don't come from visualizing victory. They're the result of a lifetime spent visualizing defeat and figuring out how to prevent it. Like most astronauts, I'm pretty sure that I can deal with what life throws at me because I've thought about what to do if things go wrong, as well as right. That's the power of negative thinking.

Life off Earth is in two important respects not at all unworldly: you can choose to focus on the surprises and pleasures, or the frustrations. And you can choose to appreciate the smallest scraps of experience, the everyday moments, or to value only the grandest, most stirring ones.

Decide in your heart of hearts what really excites and challenges you, and start moving your life in that direction

Early success is a terrible teacher. You're essentially being rewarded for a lack of preparation, so when you find yourself in a situation where you must prepare, you can't do it. You don't know how.

Other anatomical changes associated with long-duration space flight are definitely negative: the immune system weakens, the heart shrinks because it doesn't have to strain against gravity, eyesight tends to degrade, sometimes markedly (no one's exactly sure why yet). The spine lengthens as the little sacs of fluid between the vertebrae expand, and bone mass decreases as the body sheds calcium. Without gravity, we don't need muscle and bone mass to support our own weight, which is what makes life in space so much fun but also so inherently bad for the human body, long-term.

It's good to have a fear of heights. I mean, it's kind of crazy not to because if you just lean out a little bit and there's a gust of wind or somebody bumps you or something and you fall, you're splat.

Almost everything worthwhile carries with it some sort of risk, whether it's starting a new business, whether it's leaving home, whether it's getting married, or whether it's flying in space.