There is one investment mistake that celebrity investor Kevin O’Leary will never make again.

“When I was a young Buckaroo trader, I used margins and I got slaughtered. And I never did it again,” he said in a recent interview on CNBC’s “Squawk Box Asia.”

Margin investing involves borrowing money from a broker to buy stocks or other assets. This offers greater gains when the price of a stock is rising, but also increases risks when stocks fall.

“I do believe that every generation gets taught a lesson with margin, including me,” said the venture capitalist, who is also co-host of “Shark Tank” and chairman of O’Shares ETFs.

“You can tell every young investor that’s never seen a bear market … but until they experience the fear, the darkness and getting completely wiped down of their account, that’s how you learn.”

“I think it’s very important that young traders learn that and they’re learning it right now.”

A bear market is when the overall stock market drops in value by 20% or more from its recent highs. Just last week, the S&P 500 fell more than 21% below its all-time record close set in January.

O’Leary added that margin trading is “a very, very, very complicated concept for investors.”

“They don’t understand it till they get wiped out to zero on margin calls and that’s happening in every sector, particularly crypto right now,” he said.

“Grown men are weeping on the crypto place.”

Last Monday, the market cap of crypto fell below $1 trillion, down from $3 trillion at its peak in November 2021 as trading platforms halted withdrawals, companies cut jobs and panicked investors dumped their holdings.

Over the weekend, bitcoin plunged below its 2017 high, falling as low as $17,601.58.