To achieve long-term success over many financial market and economic cycles, observing a few rules is not enough. Too many things change too quickly in the investment world for that approach to succeed. It is necessary instead to understand the rationale behind the rules in order to appreciate why they work when they do and don't when they don't.

Why should the immediate opportunity set be the only one considered, when tomorrow's may well be considerably more fertile than today's?

You must buy on the way down. There is far more volume on the way down than on the way back up, and far less competition among buyers. It is almost always better to be too early than too late, but you must be prepared for price markdowns on what you buy.

The overwhelming majority of people are comfortable with consensus, but successful investors tend to have a contrarian bent.

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.

It is crucial to have a strategy in place before problems hit, precisely because no one can accurately predict the future direction of the stock market or economy. Value investing, the strategy of buying stocks at an appreciable discount from the value of the underlying businesses, is one strategy that provides a road map to successfully navigate not only through good times but also through turmoil.

When excesses such as lax lending standards become widespread and persist for some time, people are lulled into a false sense of security, creating an even more dangerous situation. In some cases, excesses migrate beyond regional or national borders, raising the ante for investors and governments. These excesses will eventually end, triggering a crisis at least in proportion to the degree of the excesses. Correlations between asset classes may be surprisingly high when leverage rapidly unwinds.