Since I retired, I very much enjoy watching Serena Williams play. While I was playing, she was one of the toughest players I ever faced. Her ground strokes are so solid, her serve is one of the most powerful in women's tennis, and mentally she is just so strong.

For me, the biggest thing with money has always been independence - just the biggest.

I lost my dad way too early and it was agonisingly awful. I missed him so much and I hated knowing that I could never again pick up the phone to tell him about my day.

I'm about the present.

The person who makes a success of living is the one who sees his goal steadily and aims for it unswervingly.

My books have occasionally been of mixed success. It's not like I have gone from triumph to triumph. I have had a couple of books do very, very well and a couple do very, very badly.

Sticking to good habits can be hard work, and mistakes are part of the process. Don't declare failure simply because you messed up or because you're having trouble reaching your goals. Instead, use your mistakes as opportunities to grow stronger and become better.

Our output and continued success is all about our culture. Ours has to be highly collaborative, and we have company-wide events and processes to make sure everyone stays aligned.