There have been times where, let's say on LGBT issues, when we were trying to end Don't Ask, Don't Tell, and I got the Pentagon and Bob Gates, a Republican holdover from the [George W.] Bush administration, to authorize a study of how you might end Don't Ask, Don't Tell, headed up by Jeh Johnson, who at that time was a council to the Justice Department. And it was going to take a year to conduct that study, issue a report, and figure out how it might be implemented, what effect it would have on unit cohesion and military effectiveness.

I think I did in the sense that there's a whole generation coming up behind us that was engaged, inspired, worked for change during the course of my presidency, saw what was possible. And that generation, it's coming.

There's no doubt that probably at least once a week, maybe once a day, I said, "Ah, I should have done that better."

If there's one thing I would like to see, it'd be for us to be able to price the cost of carbon emissions.

To those of you mourn the loss of a loved one today, my heart goes out to you. We remember that the blessings that we enjoy as Americans came at a dear cost. Our nation owes a debt to its fallen heroes that we cannot ever fully repay. But we can honor their sacrifice, and we must. We must honor it in our own lives by holding their memories close to our hearts, and heeding the example they set.

It's time to fundamentally change the way that we do business in Washington. To help build a new foundation for the 21st century, we need to reform our government so that it is more efficient, more transparent, and more creative. That will demand new thinking and a new sense of responsibility for every dollar that is spent.

Presidential elections always turn on personalities, they turn on how campaigns are run, they turn on natural desires for change.