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.

I wasn’t destined to be an astronaut. I had to turn myself into one.

When I stand on the edge of a cliff or right at the edge of a building or something, it's one of the few things that gives me kind of a deep, overwhelming, irrational fear where it affects my physiology.

The cool things about space is when you put your pants on here, you can put them on two legs at a time.

The danger is different from the fear. ... [practice] what to do if things go wrong, as well as right.

I'm not a wealthy person and I don't think that I would be able to prioritize that much money to go for a ride to a place that I have already lived. But if the price comes down or I win a lottery or something, why not?

By looking at the difference between perceived danger and actual danger, you can fundamentally change your reaction.