Warren Buffett, who's known as one of the best investors in the world, made a mistake with his first investment when he was just 11 years old.
He and his sister bought shares in a company called Cities Service, but the price went down quickly, and he got worried.
He decided to sell the shares for a small profit, but he missed out on a much bigger gain when the price of the stock went up significantly later.
This experience taught him a valuable lesson about investing: patience and long-term thinking are essential for success.
