This line is from Warren Buffett, American investor and Chairman of Berkshire Hathaway. Buffett, who never bets for the short-term, is considered one of the most successful investors in the world, and has an approximate net worth of Us $82 billion, which makes him the third-wealthiest person internationally. 

Buffett's investing philosophy is, "Don't lose money". But he personally lost about $23 billion in the financial crisis of 2008, and his company lost its AAA ratings. So what does this mean? Buffett's argument is about mindset - don't play to lose when it comes to the stock market. Do your homework. Don't gamble, don't invest like it's a card game. 

Buffett believes the most important quality for an investor is not intelligence, but attitude and approach to the stock market, and a willingness to show patience. A good investor focuses on their own goals rather than being swayed one way or another by the crowd. Markets will swing. That's the nature of the market. But up or down, the investor keeps to the strategy that they have found works for them. And the strategy tends to be a long-term, patient one.