"Well, one time some attractive woman sat next to Charlie and asked him what he owed his success to, and, unfortunately, she insisted on a one word answer. He had a speech prepared that would have gone on for several hours. But when forced to boil it down to one word, he said that was "rational". You know, he comes equipped for rationality, and he applies it in business. He doesn't always apply it elsewhere, but he applies it in business and that has made him a huge business success."

Source: Warren Buffett Reveals A 6th Rule For Investing by Sam Ro, www.businessinsider.com. March 1, 2014.