I read that at a key fork in the road moment for me where I just sold CD Baby and had a ton of money. I was like, “What to do now?” And I read this book from this filthy rich old man being entirely honest, and I thought I should just learn from his experience. ... So if what I’m doing seems weird, it’s because I took his advice to heart and I’ve quit the game.

So, it was hard to fathom letting go. Age was part of the reason. We were both 77 at that time.

No, because I was set for it. My core, my whole life was medicine. I wanted to become a specialist. So for ten years I concentrated solely on medicine. It took ten years to become a consultant in neurology.

I have never liked the word retirement. It doesn't feel like a modern word to me. I've been thinking of this as a transition, but I want to be sensitive about how I use that word, which means something very specific and important to a community of people. Maybe the best word to describe what I'm up to is evolution. I'm here to tell you that I'm evolving away from tennis, toward other things that are important to me.

That’s an easy question. It was, of course, George Balanchine. He came from Russia via Europe and settled in America in 1933. He started a little company which was not very successful, so he had to start over and over again. Ultimately, he founded the New York City Ballet. I happened to be born at the right time, came to the right place, and had the fortune to audition for him, and work with him, because he is the genius of the century of ballet. I learned how to dance with him.

Well, I’ve had injuries, but I’d always get out on stage because I think the body is a wonderful thing, and you have to treat it with respect. We haven’t even reached our potential for what we can do as human beings. I went through a period where I had hip trouble. I thought it was just a typical pulled muscle, so I used liniment, and warmed up more than I thought was necessary, all the things we learn to do when you have a typical dance-related injury or sore muscle. Over the months, it didn’t go away. In fact, it got worse. Eventually I realized that I had a very serious problem, and it was the first time that dance had let me down. What had been my salvation and my security with my body was abandoning me. This was emotionally and physically devastating.

No, never. Strangely enough, being such a tomboy, and being so—as my mother says—spoiled as a child, once I started dancing and in a way growing up, I was not the spoiled brat or the rebellious child that I was when I really had no reason to be as a child. When you work, it’s a laboratory. The dance studio, when we were working together, was the place where you experiment. I’m not intimidated by failure or making a mistake, because you learn from those situations. You don’t learn from a situation where you do something well. You enjoy it and you give yourself credit, but you don’t really learn from that. You learn from trial and error, trial and error, all the time. When you fail, maybe you failed in that particular instance, but you have discovered something else. A lot of the ballets that we went on to do were built around mistakes that we had made in the classroom. So you never throw anything out. Rebelling takes up energy. As a dancer, you don’t have that kind of energy to throw away.

I think he was a great philosopher. He had a wonderful theory that you live in the “now,” which I think is important. Along with living in the moment, you also have to assume the responsibility that goes along with it, and you don’t take your position lightly. But it also means that you get the full value of the moment that you are living, so you don’t look back on your life and say, “If only I hadn’t wasted time, if only I had done this.” You do the best you can. It was wonderful to be able to go home after a performance, and think, well it wasn’t maybe so good, but it was the best I could be at that time.