US Airways Capt. Chesley "Sully" Sullenberger has flown thousands of flights in the last 42 years. "But now," he says, "my entire career is being judged by how I performed on one of them."

That flight, of course, came last Jan. 15, when his Airbus A320 suffered a bird strike en route from New York to Charlotte, N.C., and lost both engines. Sully and First Officer Jeff Skiles executed an emergency landing later dubbed "The Miracle on the Hudson," but that description never felt right to Sully.

In January, Capt. Chesley Sullenberger successfully landed US Airways flight 1549 into the Hudson River after it collided with birds, causing both engines to fail. He discusses how the event has offered a message of hope to many.

He is a precise, methodical, cerebral man who carefully chooses his words. In recent months, while working on his new book, "Highest Duty: My Search for What Really Matters," Sully spent a great deal of time reviewing his life and career. He has tried to understand what experiences from his past prepared him for Flight 1549.

As Sully's co-author, I clearly saw that it wasn't only his skills as a veteran pilot that carried him in those tense moments over Manhattan. It was also his upbringing, his family bonds, his sense of integrity—and his own losses. Flight 1549 wasn't just a five-minute journey from LaGuardia Airport to the Hudson. Sully's entire life led him to safely to that river.

He was born in Denison, Texas, the son of a dentist and a teacher who had high expectations. "I grew up in a home where each of us had our own hammer," says Sully. That was because his dad kept enlarging the family home with the help of three not-always-willing assistants: Sully, his sister and his mom. "The goal was to do everything ourselves, to learn what we didn't know and then have at it," Sully says. The house wasn't perfect, but Sully knew where every nail was.

"Sometimes I'd brood, wishing we lived in a professionally built house like everyone else," he says. "But each time the house grew, I felt a sense of accomplishment."

Chesley Sullenberger at about eight years old, with a model airplane he received for Christmas. Captain Chesley Sullenberger

As a boy, Sully was a classic introvert who felt things deeply. In 1964, for instance, he saw news reports about a New York woman named Kitty Genovese. Her neighbors heard her screams as she was being stabbed to death by a stranger outside her apartment. Allegedly, they did nothing to help.

"I made a pledge to myself, right then at age 13," Sully recalls, "that if I was ever in a situation where someone such as Kitty Genovese needed my help, I would choose to act. No one in danger would be abandoned. As they'd say in the Navy: 'Not on my watch.' "

People tell Sully that his success on Jan. 15 showed a high regard for life. Their words led him to reflection. "Quite frankly," he says, "one of the reasons I think I've placed such a high value on life is that my father took his."

Suffering from depression, Sully's father killed himself in 1995. "His death had an effect on how I view the world," he says. "I am willing to work hard to protect people's lives, to not be a bystander, in part because I couldn't save my father."

There are other moments in Sully's personal life that he feels helped prepare him for Flight 1549. Sully and his wife struggled with infertility, then endured the arduous journey of trying to become adoptive parents. "The challenges Lorrie and I faced made me better able to accept the cards I've been dealt," Sully says, "and to play them with all the resources at my disposal." The couple eventually adopted two daughters, now ages 16 and 14.

He first yearned to fly at age five. At 16, in 1967, he began taking lessons from a no-nonsense crop-dusting pilot named L.T. Cook Jr.

Sully was an earnest, hard-working student who paid close attention. One day he noticed a crumpled Piper Tri-Pacer at the end of Mr. Cook's grass airstrip. A friend of Mr. Cook's had tried to land the plane and didn't realize that power lines stretched across a nearby highway. The plane slammed into the ground nose first. The pilot died instantly.

Sully peered into the blood-splattered cockpit. "I figured his head must have hit the control panel with great violence," he says. "I tried to visualize how it happened—his effort to avoid the power lines, his loss of speed, the awful impact. I forced myself to look into the cockpit, to study it. It would have been easier to look away, but I didn't."

Chesley Sullenberger, about to board his first flight in a military jet. Captain Chesley Sullenberger

That sobering moment taught Sully to be vigilant and alert. For a pilot, one simple mistake could mean death.

He went on to the U.S. Air Force Academy, then a military career, and continued to study accidents. Twelve fellow military pilots died on training runs. "I grieved for my lost comrades," he says, "but I tried to learn all I could about each of their accidents."

As an airline pilot, he helped develop an air-safety course and served as an investigator at crash sites. He'd page through transcripts from cockpit voice recorders, with the last exchanges of pilots who didn't survive.

Since childhood, Sully has been fascinated by Charles Lindbergh. In "We," Lindbergh's 1927 book, he explained that his success was due almost entirely to preparation, not luck. "Prepared Lindy" wouldn't have had the same magic as his nickname "Lucky Lindy," but his views resonated with Sully.

One aspect of preparing well is having the right mindset, he says. "In so many areas of life, you need to be a long-term optimist but a short-term realist. That's especially true given the inherent dangers in aviation. You can't be a wishful thinker. You have to know what you know and don't know, and what your airplane can and can't do in every situation."

Sully has always kept in mind the air-crew ejection study he learned about in his military days. Many pilots waited too long before ejecting from planes that were about to crash. They either ejected at too low an altitude, hitting the ground before their parachutes could open, or they went down with their planes.

Why did these pilots spend extra seconds trying to fix the unfixable? The answer is that many feared retribution if they lost million-dollar jets. And so they remained determined to try to save their airplanes.

Sully says he has never shaken his memories of fellow Air Force pilots who didn't survive such attempts. Having those details in the recesses of his brain was helpful as he made quick decisions on Flight 1549. "As soon as the birds struck," he says, "I could have tried to return to LaGuardia so as not to ruin a US Airways aircraft. I could have worried that my decision to ditch the plane would be questioned by superiors or investigators. But I chose not to."

Sully values the concept of "goal sacrificing." When it's no longer possible to complete all your goals, you sacrifice lower-priority goals. He instinctively knew that goal-sacrificing was paramount on Flight 1549. "By attempting a water landing," he says, "I would sacrifice the 'airplane goal'—trying not to destroy an aircraft valued at $60 million—for the goal of saving lives."

Able to compartmentalize his thinking, even in those dire moments over the Hudson, Sully says his family did not come into his head. "That was for the best. It was vital that I be focused; that I allow myself no distractions. My consciousness existed solely to control the flight path."

Since saving 155 lives that day, Sully has received thousands of emails and now has 635,000 Facebook fans. His actions touched people so deeply that they felt compelled to reach out and share their own seminal experiences with him.

Adapted from "Highest Duty: My Search for What Really Matters," by Capt. Chesley "Sully" Sullenberger with Jeffrey Zaslow. Copyright 2009 by Chesley B. Sullenberger III. Published by William Morrow/HarperCollins Publishers. Patrick Conlon / The Wall Street Journal

"I am now the public face of an unexpectedly uplifting moment," Sully says, and he accepts that. Still, he's not comfortable with the "hero" mantle. A hero runs into a burning building, he says. "Flight 1549 was different because it was thrust upon me and my crew. We turned to our training, we made good decisions, we didn't give up, we valued every life on that plane—and we had a good outcome. I don't know that 'heroic' describes that. It's more that we had a philosophy of life, and we applied it to the things we did that day."

Sully has heard from people who say preparation and diligence are not the same as heroism. He agrees.

One letter that was particularly touching to Sully came from Paul Kellen of Medford, Mass. "I see a hero as electing to enter a dangerous situation for a higher purpose," he wrote, "and you were not given a choice. That is not to say you are not a man of virtue, but I see your virtue arising from your choices at other times. It's clear that many choices in your life prepared you for that moment when your engines failed.

"There are people among us who are ethical, responsible and diligent. I hope your story encourages those who toil in obscurity to know that their reward is simple—they will be ready if the test comes. I hope your story encourages others to imitation."

Sully now sees lessons for the rest of us. "We need to try to do the right thing every time, to perform at our best," he says, "because we never know what moment in our lives we'll be judged on."

He always had a sense of this. Now he knows it for sure.

Write to Jeffrey Zaslow at jeffrey.zaslow@wsj.com