Whatever it is, people have issues and that affects you deeply. So you have to get to the bottom of it and not let that affect your life decisions and really understand why you're making the decisions you make so that way you can understand how to not do that, so I always encourage people to ask why and then to really understand you, because that's the only way to be your most successful and your most happy.

A lot of people say, "Oh, I get this high from working out." I've never felt that, maybe because I've worked out for so long it's just a norm for me to push super, super hard. I don't feel the euphoria. But at the end, when it's all done, I feel euphoric. I'm like, "Yes, the work is done." You just feel like a glowing feeling inside.

My ambition is to enjoy my life and to do exactly what I want to do. And I'll do that. I will be free.

Winning once is never anyone's dream. We all want to keep winning no matter what it is, or if we retire, we all still are striving toward something, probably most of us are.

I believe I live in a black and white. I think things are like either black or white. I don't really believe that much in the gray. I think that there's gray for a lot of people, but I don't live in the gray. I realize whatever action I have or take, it's going to have a consequence -- either good or bad. So I live my life in a way where I don't have bad consequences. I just notice there's a lot people around me just live in the gray. I don't know, for me, I'm just really straightforward.

I just try to stay positive and focused on the tennis, not let anything get to me, like crazy questions. But I'm tough, let me tell you, tough as nails.

Everything is tennis for me, it's my career and it's entertainment, but it's also a business.