John “Jack” Bogle, founder of the Vanguard Group, has a life lesson for investors: The only thing worse than making a mistake is refusing to admit it.

"I always thought I looked better admitting a mistake," Bogle said at a portfolio manager conference in New York, CNBC.com reported.

Bogle made his biggest investment mistake when he merged the storied mutual fund company he was running, Wellington Funds, with a company in Boston that embraced portfolios heavily laden with risky equities. Wellington lost money, and the board fired Bogle, CNBC.com explained.

"My decisions were not quite as stupid as you might think. I was trying to save the company," Bogle said. "Now, that's a little bit of an excuse, and I admit that," he said.

Bogle then went on to launch Vanguard.

Bogle has another guideline for separating mistakes from failed experiments, which happen often when you're building a company, CNBC reported. "Look around and see if you've done material damage to something that already existed. "When something results in a catastrophe, it's like those people who say, 'I wouldn't have done anything differently.' ... Well, yes, if the house burned down, yes, you should have," he said.  

Bogle started the indexing revolution for retail investors in 1976 when he launched the Vanguard 500 Index Fund. The fund, which just passed its 40th anniversary, had $205 billion in assets as of Aug. 31. 

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