We need to have mentors. I think I've always been pretty shameless about seeking out people much smarter and much more experienced than me from the very beginning. Michael Seibel and other people. And the more successful I got, the more leaders I started seeking out, whether it was investors, or Sheryl Sandberg at Facebook, or I got the opportunity to spend time with Warren Buffett and he became a close mentor of mine.

My training took seven years. I didn’t learn how to make sushi for the first three years. I only got two days off a month, and slept on the restaurant floor. But I loved the job. I’d go to the fish market every morning. I got to open the restaurant and see the customers. I’d watch my mentor making sushi and would copy him under the table, practising with my fingers.

Remember, if you sit at your desk for 15 or 20 years, every day, not ­counting weekends, it changes you. It just does. It may not improve your temper, but it fixes something else. It makes you more free.

Of all the gifts that tennis has given me over the years, the greatest, without a doubt, has been the people I've met along the way: my friends, my competitors, and most of all the fans who give the sport its life.

The questions of the students are often the source of new research.  They often ask profound questions that I’ve thought about at times and then given up on, so to speak, for a while.  It wouldn’t do me any harm to think about them again and see if I can go any further now.  The students may not be able to see the thing I want to answer, or the subtleties I want to think about, but they remind me of a problem by asking questions in the neighborhood of that problem.  It’s not so easy to remind yourself of these things.

It was a brilliant idea: You have no responsibility to live up to what other people think you ought to accomplish.  I have no responsibility to be like they expect me to be.

It is necessary, I believe, to accept this idea, not only for science, but also for other things; it is of great value to acknowledge ignorance.  It is a fact that when we make decisions in our life we don't necessarily know that we are making them correctly; we only think that we are doing the best we can – and that is what we should do.

So I got this new attitude.  Now that I am burned out and I’ll never accomplish anything, I’ve got this nice position at the university teaching classes which I rather enjoy, and just like I read the Arabian Nights for pleasure, I’m going to play with physics, whenever I want to, without worrying about any importance whatsoever.

Nothing happens because there’s not enough real activity and challenge: You’re not in contact with the experimental guys.  You don’t have to think how to answer questions from the students.  Nothing!

For example, I was a little surprised when I was talking to a friend who was going to go on the radio. He does work on cosmology and astronomy, and he wondered how he would explain what the applications of this work were. "Well," I said, "there aren't any." He said, "Yes, but then we won't get support for more research of this kind." I think that's kind of dishonest. If you're representing yourself as a scientist, then you should explain to the layman what you're doing—and if they don't want to support you under those circumstances, then that's their decision.