'm so fortunate to have done what I love to do for so long, but the day I retired was one of the best days of my life. Not because I was happy to get away from the sport, but because it was clear in my mind that I had done all I possibly could, and that it was time to go.

I've found that a person does not need protein from meat to be a successful athlete. In fact, my best year of track competition was the first year I ate a vegan diet.

It's all about the journey, not the outcome.

Whether I'm 40, 50 or 60, I'm going to be as physically strong as I am able.

Join me in the final race to smash poverty and achieve the UN Millennium Development Goals

I've always known that sporting people frequently suffer from joint problems because of the repeated strain they put on their bodies to get to the top. But somehow I never thought it would happen to me.

I'm not Carl Lewis the athlete any more. I'm growing into a new person with new interests and new goals.