"It's not personal, Sonny. It's strictly business." Michael Corleone's retort to his brother in "The Godfather" is also good advice for your investments.
Sam Stovall, chief equity strategist at S&P Capital IQ and the son and grandson of money managers, told CNBC on Tuesday that he doesn't let his emotions rule his stock picks.
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"In this day and age of instant information, I can experience both fear and greed at the exact same moment," he said in a "Squawk Box" interview. "So I will frequently use history as virtual valium."
Watch Stovall explain the three reasons why he keeps emotions out of his investment choices and how market history may help ease your mind about when to get in or out of the stock market.