Excerpt from It's Not About the Bike by Lance Armstrong, Sally Jenkins, plus links to reviews, author biography & more

Cancer is like that, too. Good, strong people get cancer, and they do all the right things to beat it, and they still die. That is the essential truth that you learn. People die. And after you learn it, all other matters seem irrelevant. They just seem small.

I don't know why I'm still alive. I can only guess. I have a tough constitution, and my profession taught me how to compete against long odds and big obstacles. I like to train hard and I like to race hard. That helped, it was a good start, but it certainly wasn't the determining factor. I can't help feeling that my survival was more a matter of blind luck.

When I was 16, I was invited to undergo testing at a place in Dallas called the Cooper Clinic, a prestigious research lab and birthplace of the aerobic exercise revolution. A doctor there measured my VO2 max, which is a gauge of how much oxygen you can take in and use, and he says that my numbers are still the highest they've ever come across. Also, I produced less lactic acid than most people. Lactic acid is the chemical your body generates when it's winded and fatigued -- it's what makes your lungs burn and your legs ache.

Basically, I can endure more physical stress than most people can, and I don't get as tired while I'm doing it. So I figure maybe that helped me live. I was lucky -- I was born with an above-average capacity for breathing. But even so, I was in a desperate, sick fog much of the time.

My illness was humbling and starkly revealing, and it forced me to survey my life with an unforgiving eye. There are some shameful episodes in it: instances of meanness, unfinished tasks, weakness, and regrets. I had to ask myself, "If I live, who is it that I intend to be?" I found that I had a lot of growing to do as a man.

I won't kid you. There are two Lance Armstrongs, pre-cancer, and post. Everybody's favorite question is "How did cancer change you?" The real question is how didn't it change me? I left my house on October 2, 1996, as one person and came home another. I was a world-class athlete with a mansion on a riverbank, keys to a Porsche, and a self-made fortune in the bank. I was one of the top riders in the world and my career was moving along a perfect arc of success. I returned a different person, literally. In a way, the old me did die, and I was given a second life. Even my body is different, because during the chemotherapy I lost all the muscle I had ever built up, and when I recovered, it didn't come back in the same way.

The truth is that cancer was the best thing that ever happened to me. I don't know why I got the illness, but it did wonders for me, and I wouldn't want to walk away from it. Why would I want to change, even for a day, the most important and shaping event in my life?

People die. That truth is so disheartening that at times I can't bear to articulate it. Why should we go on, you might ask? Why don't we all just stop and lie down where we are? But there is another truth, too. People live. It's an equal and opposing truth. People live, and in the most remarkable ways. When I was sick, I saw more beauty and triumph and truth in a single day than I ever did in a bike race -- but they were human moments, not miraculous ones. I met a guy in a fraying sweat suit who turned out to be a brilliant surgeon. I became friends with a harassed and overscheduled nurse named LaTrice, who gave me such care that it could only be the result of the deepest sympathetic affinity. I saw children with no eyelashes or eyebrows, their hair burned away by chemo, who fought with the hearts of Indurains.

I still don't completely understand it.

All I can do is tell you what happened.

Reprinted from IT’S NOT ABOUT THE BIKE by Lance Armstrong with Sally Jenkins by permission of G. P. Putnam’s Sons, a member of Penguin Putnam Inc. Copyright © 2000 by G.P.Putnam’s Sons. All rights reserved. This excerpt, or any parts thereof, may not be reproduced in any form without permission.