Here’s Mark Cuban’s sobering advice for Redditors who have lost money on GameStop stock

As shares of GameStop continued to fall for the second day in a row on Tuesday, billionaire Mark Cuban offered words of wisdom to Reddit users who may have seen their fortunes take a turn for the worse after last week’s astounding rally.

“I learned some expensive lessons when I first started trading stocks,” the Shark Tank investor said during an AMA session when asked what advice he had for people who have lost money over the last few weeks. “It was painful. But I tried to learn what I got right and wrong. Right now, right here. The game is changing. The hard part is ask yourself if what you believed in has actually changed.”

The AMA session took place on the WallStreetBets forum where an army of retail investors have been steadfastly pumping up GameStop stock at the expense of Wall Street hedge funds that had bet against it. At its high point last week, shares of the video-game retailer hit $483, a phenomenal rise from only about $17 a share at the beginning of this year.

But the stock has since begun to collapse, in part because brokerages like Robinhood halted or limited trading last week amid the frenzy. GameStop was down more than 40% in early trading Tuesday.

In his AMA, Cuban said one of the keys to smart investing is playing the long game, but traders should also truly believe in the value of what they buy. As an example, he cited bitcoin, which has shown huge volatility over the years, but is now finally starting to gain the support of mainstream financial services like PayPal and others.

“Many bought [bitcoin] at the highs in 2017 and watched it fall by 2/3 or more,” Cuban wrote. “But they held on because they believed in the asset.”

“The same applies to stocks,” he said. “When I buy a stock I make sure I know why I’m buying it. Then I HODL [until] I learn that something has changed. The price may go up or down, but if I still believe in the logic that made me buy the asset, I don’t sell. If something changed that I didn’t expect, then I look at selling.”

The entire AMA thread is worth a read. You can check it out here.

Quotes in this story were lightly edited for punctuation and style.