I was lucky enough to win the Davis Cup in my first year in 1999. I won my first slam at the U.S. Open in 2001 and became world No. 1 later that year. By the age of 20, I'd done it all.

I'm one injury away from hanging up the racket at any time.

I am two different people. What you see on the court is just natural for me. I wear my heart on my sleeve. I have always said 'C'mon' purely to fire myself up. Off the court, I am a lot shyer. I stick to my team and my family and people I trust.

When I go out to play, I still believe I'm as good as anyone out there. I don't have to prove anyone wrong. I know what I've done and how well I can play.

(Andy Roddick's) a different kind of guy. I don't spend a lot of time with him. His coach in the past (Tarik Benhabiles), I didn't have a lot of time for at all. He was a bigger problem than Andy.

I feel like when I'm match tough and match hard and played a lot of matches I got that competitive winning spirit going and I can get on some rolls like I did last year. I won San Jose, Indian Wells and made the semifinals in Miami so it can happen for me.

I'm more in that Rafa Nadal high-energy high-octane mold out there. I wear that emotion on the court. That's how I play my best tennis. People either like that or not. And I can't change that: that's who I am on a tennis court.