If you're a champion, you have to have it in your heart. You can have the greatest coaches in the world, all the opportunities to play, and the greatest equipment, but if you don't have it inside, you're not going to make it. On the other hand, if you don't have any of those luxuries but you have heart and courage and the guts to go out there and grind it out, then you'll make it.

Ninety percent of my game is mental. It's my concentration that has gotten me this far. I won't even call a friend on the day of a match. I'm scared of disrupting my concentration. I don't allow any competition with tennis.

If you can react the same way to winning and losing, that's a big accomplishment.

After being at the top, I don't think I could play senior tournaments, because you know how good you were. I don't know if I would enjoy that, being half of what I was.

I still have this image: I can't be controversial, I can't say things.

Relationships are give-and-take, and when you're a tennis player, you're certainly not giving. You have to be self-absorbed. It has to be about you.

Once you've been number one, you can never be satisfied with less.