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.

I can definitely say the same thing [discussing Steffi Graf's claim that she had played against at least one top player who used steroids]. Steroids can really make a difference, physically and mentally. I'd be really disappointed if I had been ranked No. 2 behind someone who took steroids.

Being famous before you've formed your personality, before you have that self-esteem, is dangerous.

Losing hurts me. I was determined to be the best.

Losses are always a relief. They take a burden off me, make me feel more normal. If I win several tournaments in a row I get so confident I'm in a cloud. If I lose I go back to the dressing room and I'm no better nor worse than anyone else. A loss gets me eager again.

I'm not an overly ambitious person; I don't feel like I have to excel.

In tennis, at the end of the day you're a winner or a loser. You know exactly where you stand... I don't need that anymore. I don't need my happiness, my well-being, to be based on winning and losing.