In all of the movie portrayals, a spacewalking suit seems sort of insignificant, like a pair of shorts and a T-shirt. No one thinks much about it. But it's a spaceship, not a spacesuit, an entire life-support mechanism that's incredibly complex and cumbersome. It's very difficult to put on and off. You have to run it the whole time you are wearing it, and it redefines how you move. It's like if you put on a wetsuit and a snowmobile suit and froze yourself solid and then tried to go and do work.

Still, I also know that most people, including me, tend to applaud the wrong things: the showy, dramatic record-setting sprint rather than the years of dogged preparation or the unwavering grace displayed during a string of losses. Applause, then, never bore much relation to the reality of my life as an astronaut, which was not all about, or even mostly about, flying around in space.

I've been lucky enough to fly to space twice.

Decide in your heart of hearts what really excites and challenges you, and start moving your life in that direction. Every decision you make, from what you eat to what you do with your time tonight, turns you into who you are tomorrow, and the day after that. Look at who you want to be, and start sculpting yourself into that person. You may not get exactly where you thought you'd be, but you will be doing things that suit you in a profession you believe in. Don't let life randomly kick you into the adult you don't want to become.

If you haven't learned to ride a bike by the time your peer group has, then suddenly it's an embarrassment and you'll avoid opportunities where you're expected to ride a bike. And then it starts shaping your behaviour. Reading is much subtler, but much more destructive if you have not - for whatever reason - learned to read by the time you should.

It’s not enough to shelve your own competitive streak. You have to try, consciously, to help others succeed.

One Chief Astronaut used to make a point of phoning the front desk at the clinic where applicants are sent for medical testing, to find out which ones treated the staff well-and which ones stood out in a bad way. The nurses and clinic staff have seen a whole lot of astronauts over the years, and they know what the wrong stuff looks like. A person with a superiority complex might unwittingly, right there in the waiting room, quash his or her chances of ever going to space.