Few challenges facing America and the world are more urgent than combating climate change. The science is beyond dispute and the facts are clear.

On Syria, it's clear that the indiscriminate attacks on civilians by the [Bashar] Assad regime and Russia will only worsen the humanitarian catastrophe and that a negotiated end to the conflict is the only way to achieve lasting peace in Syria.

The campaign was a more significant training ground than I think people give it credit for. By the time I got here, I think I had a pretty good sense of what was required. But the circumstances in which I came in were different than most executives, right? The enterprise was in the midst of a major crisis.

Heaven forbid we've got a problem where we could have prevented a terrorist attack or apprehended someone who is engaged in dangerous activity, but we didn't do so simply because of inaction in the Senate.

I was watching a documentary that during the Bay of Pigs crisis JFK had about two weeks before anybody reported on it. Imagine that. I think it's fair to say that if something like that happens under a current president, they've got to figure out in about an hour what their response is.

There's no doubt that I'm a better president now than when I first took office. This is not a job where there's a manual, and over time you get a better sense of what's important, what's not, how to see around corners and anticipate problems, as opposed to just managing problems once they've arrived.

But at the end of the day, the circumstances of your life what you look like, where you come from, how much money you have, what you've got going on at home that's no excuse ... Where you are right now doesn't have to determine where you'll end up. No one's written your destiny for you. Here in America, you write your own destiny. You make your own future.