Vanguard founder Jack Bogle, who died on January 16 at the age of 89, is properly known as the inventor of the index fund and an investing genius. But Bogle was also an inspiring figure who prospered after failure and got stronger, not weaker, when he encountered adversity.

I profiled Bogle in my 2012 book Rebounders: How Winners Pivot from Setback to Success. I knew Bogle had started Vanguard in the 1970s after some kind of falling out at another financial firm. But as I did more research and interviewed Bogle at his office outside Philadelphia, I realized Bogle had the enviable ability to learn from setbacks and turn adversity to his advantage. He was persistent, but more than that, he found new opportunities amid gloomy times that would sink many of us.

Bogle was a financial whiz who only started Vanguard because he lost a boardroom battle at another company he was running, Wellington Management, which fired him in 1974. He didn’t march out and incorporate Vanguard the next day. He moped and wondered what to do next.

On a train one day, Bogle broke down in tears, overwhelmed with stress. “I was totally wiped out,” he told biographer Robert Slater. “I don’t recall another time like that, when I was wiped out by it all.”

The Vanguard origin story is well-known, but somewhat forgotten is the ferocious resistance Bogle met when he became a prophet of low-fee, passive investing. Those lower fees meant less income for brokers and dealers, and the industry attacked him, lampooning his lowly index fund as “Bogle’s Folly.” There were many points at which Bogle might have justifiably quit. Skeptical investors ponied up far less money for his fund at the outset than he hoped for, leaving him barely enough to work with. The Securities and Exchange Commission imposed regulatory barriers that nearly killed the firm. Competitors trashed Vanguard in the press. And all this happened in the 1970s as the stock market was doing lousy and double-digit inflation spooked investors.

“Nobody ever would have imagined that that wouldn’t be the end of me.”

Oh yeah, Jack Bogle also had a chronically weak heart. He had his first heart attack in 1969, at age 31. He would eventually have six heart attacks, and receive a transplanted heart in 1996.

Years later, I asked Bogle what kept him going when he was tempted to give up. He told me about the Greek myth of Antaeus, the son of Poseidon, who had gained fame as an unbeatable wrestler. Antaeus’s secret was that he gained indomitable strength when he was in contact with the ground, which meant he got stronger when knocked down. Bogle felt he, too, had gained strength from a smackdown. “When I got fired,” he said, “nobody ever would have imagined that that wouldn’t be the end of me.”