Big Mistakes: The Best Investors and Their Worst Investments (Bloomberg)

by Michael Batnick

Making money in the stock market is difficult. Whether you're running a hedge fund or your own brokerage account, there will be times when you feel really foolish.

The most important thing successful investors have in common is worrying about what they can control. They don't waste time worrying about which way the market will go or what the Federal Reserve will do or what inflation or interest rates will be next year. They stay within their circle of competence, however narrow that might be. Warren Buffett said, “What counts for most people in investing is not how much they know, but rather how realistically they define what they don't know.”