Successful investors must temper the arrogance of taking a stand with a large dose of humility, accepting that despite their efforts and care, they may in fact be wrong.

There are only a few things investors can do to counteract risk: diversify adequately, hedge when appropriate, and invest with a margin of safety. It is a precisely because we do not and cannot know all the risks of an investment that we strive to invest at a discount. The bargain element helps to provide a cushion for when things go wrong.

One of the biggest challenges in investing is that the opportunity set available today is not the complete opportunity set that should be considered. Limiting your opportunity set to the one immediately at hand would be like limiting your spouse to the students you met in high school

The latest trade of a security creates a dangerous illusion that its market price approximates its true value. This mirage is especially dangerous during periods of market exuberance. The concept of "private market value" as an anchor to the proper valuation of a business can also be greatly skewed during ebullient times and should always be considered with a healthy degree of skepticism.

Investors should pay attention not only to whether but also to why current holdings are undervalued. It is critical to know why you have made an investment and to sell when the reason for owning it no longer applies. Look for investments with catalysts that may assist directly in the realization of underlying value. Give reference to companies having good managements with a personal financial stake in the business. Finally, diversify your holdings and hedge when it is financially attractive to do so.

Selling, in particular, can be a challenge; many investors are tempted to become more optimistic when a security is performing well. This temptation must be resisted; tax considerations aside, when a security reaches full valuation, there is no longer a reason to own it.

My view is that an investor is better off knowing a lot about a few investments than knowing a little about each of a great many holdings. One's very best idea's are likely to generate higher returns for a given level of risk than one's hundredth or thousandth best idea.