I've never said that troops should be withdrawn. What I've said is, is that we've got to make sure that we secure and execute the rebuilding and reconstruction process effectively and properly, and I don't think we should have an artificial deadline when to do that.

If we are not serious about facts and what's true and what's not. And particularly in an age of social media where so many people are getting their information in sound bites and snippets off their phones, if we can't discriminate between serious arguments and propaganda, then we have problems.

Reality has a way of asserting itself.

When you see a Donald Trump and a Bernie Sanders, very unconventional candidates, have considerable success, then obviously there's something there that's being tapped into; a suspicion on globalization, a desire to reign in it's excesses, a suspicion of elites and governing institutions that people feel may not be responsive to their immediate needs. And that sometimes gets wrapped up in issues of ethnic identify or religious identity or cultural identity, and that can be a volatile mix.

Going through the legislative process is always better, in part because it's harder to undo.

For the sake of our children and our future, we must do more to combat climate change. Now, it's true that no single event makes a trend. But the fact is the 12 hottest years on record have all come in the last 15. Heat waves, droughts, wildfires, floods-all are now more frequent and more intense. We can choose to believe that Superstorm Sandy, and the most severe drought in decades, and the worst wildfires some states have ever seen were all just a freak coincidence. Or we can choose to believe in the overwhelming judgment of science-and act before it's too late.

For me, personally, the most difficult moments had to do with not just terrorist attacks, but also shootings.