Even if I have already peaked, I have to believe I can improve. I wake up every morning, and go to practice, with the illusion that I'm going to get better that day.

Some people get very confused about my game. They think it's better if the court is slow, because I have a good defence. But the faster it is, the better for me. My spin is more painful for my opponents, my aggressive game works better.

I only ever run when there's some point to it - say, if it's in a game of tennis.

Even if I have already peaked, I have to believe I can improve. I wake up every morning, and go to practice, with the illusion that I'm going to get better that day.

Today people hit the ball with much more strength. Almost every player is capable of playing a winning stroke from any position. This means the balls arrive more quickly. If you want to reach them, you have to slow down from a high speed or suddenly change direction. These are moments when you can injure yourself, and that's what wears us out.

Don't think about being the number one in the world, try instead to get through today's program as well as you can. Then we will see whether one day you'll end up as number one or number 100.

If you are playing bad you are going to lose here, on clay, on ice, or on the beach.