Ron Baron told CNBC on Tuesday that investors can learn as much, if not more, from their mistakes than their successes.
Starting with Under Armour, Baron told "Squawk Box" he's made at least 10 times his money. "We recently bought, in the past week, 1.5 million [additional] shares, when the stock has come down a couple points because they lost a customer."
He started buying UA shares in 2005.
Instead of doing $5.1 billion in sales this year, Baron expects Under Armour to have $4.9 billion. But his message to investors who want to be in stocks for the long haul is: "Nobody is going to think about this in a few years."
"What I think about is the company is going to go from $5 billion to $20 billion in 10 years or eight years," he said. "When they get there, they'll make a 15 percent profit margin."
"I think we're going to make three or four times, probably four times [our money] in the next 10 years in Under Armour," said the chairman and CEO of Baron Capital, which has $21 billion in assets under management.
Patience is proving profitable for Baron with Under Armour.