The biggest challenge in the stock market is not Mr. Market or Mr. Value. The biggest challenge is neither visible nor measurable; it is hidden in the emotional incapacities of each of us as investors. Investing, like parenting teenagers, benefits from calm, patient persistence and a long-term perspective and constancy of purpose. That's why "know yourself" is the cardinal rule in investing.
The hardest work in investing is not intellectual; it's emotional. Being rational in an emotional environment is not easy, particularly with Mr. Market always trying to trick you into making changes. The hardest work is not figuring out the optimal investment policy; it's sustaining a long-term focus—particularly at market highs or market lows—and staying committed to your optimal investment policy.
-Charles D. Ellis, Winning The Loser's Game: Timeless Strategies for Successful Investing