Playing tennis, I didn't tie in my self-worth into winning or losing matches.

I just wanted to play tennis. It wasn't a job. It was an ambition. I knew I could make money at it. I was 18 - old enough to think I could do it, young enough not to consider the consequences.

I can teach many sports, but obviously, tennis is the one. When you do other sports, you see things from different perspectives: different footwork drills, body positions, angles and geometry. All that stuff is helpful, and so when I do other sports, I can see things, because once you know one sport, then the other sport becomes more clear.

So many athletes are afraid to use their platform to do the right thing and speak what they feel, and that's very depressing. Sure, they are afraid of insulting people and losing money because of it, and everyone wants to make the maximum amount of money in their lifetime. But at the expense of who you are? I don't know. That just wasn't in my DNA.

I am just sorry my own mother had to live under that regime for most of her life. I was lucky. I got out and, 14 years later, Czechoslovakia became a free country. So I feel anger, even fury, at this bloody system that ruined so many people's lives for no reason whatsoever.

When you make a lot of money, it just means you made a lot of money. It doesn't make you a better person.