When Mark Cuban first started trading stocks, he learned some "expensive lessons."
That's why he says it's important to assess your personal financial situation before trading or investing in the market, he said.
"If you are buying [a stock] because you need the price to go up and solve a financial hole you are in, that is the EXACT WRONG time to trade," Cuban tweeted on Wednesday.
"Get right and come back later," he said.
Indeed, experts recommend amassing emergency savings before taking on the risk of the stock market. Investing for the long-term in passive funds that track an index, like the S&P 500, or in mutual funds historically has better results than stock picking, research shows.
On social media, many day traders, including those from subreddit WallStreetBets, have been asking Cuban whether to hold or sell GameStop stock – after a huge surge, the video game retailer's shares are now declining, leaving many unsure of what to do with their stake.
Cuban said Tuesday during a Reddit "Ask Me Anything" that he doesn't own any GameStop stock, but if he did, he would hold.
"The price may go up or down, but if I still believe in the logic that made me buy he asset, I don't sell. If something changed that I didn't expect, then I look at selling."
Of course, "We all have to respect people who choose to sell because they need to. Bills don't care what the market does," he said in his tweet Wednesday.
Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."