Astronaut Scott Kelly knows a thing or two about endurance.

Growing up, his dream of spaceflight wasn't always within reach. A less-than-stellar student at first, his motivation to pursue spaceflight didn't come until age 18.

But even when he'd achieved that goal, the challenges persisted.

In 2011, Kelly was on the International Space Station as part of a five-and-a-half month mission when his sister-in-law, Democratic Congresswoman Gabrielle Giffords, was critically wounded during a mass shooting in Arizona. Before that, the hope had been that Kelly and his brother, Mark, also an astronaut, might meet in orbit.

His heart with his family, Kelly did his best to keep updated through Mission Control, the internet and the lone phone aboard the space station.

On Thursday night, Kelly was in Toronto for a sit-down with Canadian astronaut Dr. Dave Williams at the Ontario Science Centre to talk about his time in space, what sparked his dream, and what's next for spaceflight. CBC Toronto's Mike Wise caught up with him ahead of his appearance.

Here is part of their conversation:

A: "I think it does mean different things … One, it's about the endurance of being in space for a year and what that takes. And it's also about endurance... As a kid growing up, I wasn't the best student initially and I found motivation and inspiration from a book when I was 18. And along the way, during my career there were always opportunities to get sidetracked, but I always kind of stuck with it, had a goal, just kind of pushing forward.

Eighteen years later, from the time I read the book The Right Stuff… I'm flying in space for the first time, so I think it has meaning there for me."

Endurance, Kelly said, was also the name of Sir Ernest Shackleton's ship. ''That was a book that I used when I was in space if I ever felt like this is a hard thing to do, I'd just read a few pages from his book and I would be like, 'Ah this is easy.'"

A: "By sharing the not-so-perfect stuff, it kind of validates the good part of the story, it makes it more real, it makes it more human."

A: "I had a plan for pacing myself. Certainly I needed to do my job but there's a balance you know, you can't do everything perfectly the time, especially when you're going to be there for a year, you don't want to burn yourself out.

"I wanted to come home clearly but if they had said, 'Hey, we cant launch the Soyuz, we need you to stay another few months,' it wouldn't be a problem."

A: "You get to do this as a team with your friends, people you work with, in my case, although I've never flown with my brother, having my brother who's also flown in space, being able to share that with them. You know it's a bond between people who have had this extraordinary experience and the fact that we're able to do this together. That's why it's so great — I flew with Dave Williams and now he's going to be interviewing me about the book.

A: "To me, the biggest concern when I was in space was not my personal safety, it was really the safety of my family on the ground and if something happened to them. And especially having experienced that before firsthand when Gabby was shot. You know, what if something happened to my kids, what if something happened to my fiancée? You can't be there to help them ... And that was always my biggest concern."

A: "You know the good thing about not going to Mars? We can still dream about going to Mars. Those kids could be the first people to go to Mars someday. Had we done that back in the 70s, it would have been old hat. I'm right behind them, with them 100 per cent."