Investing is the intersection of economics and psychology. The analysis is actually the easy part. The economics, the valuation of the business isn't that hard. The psychology - how much do you buy, do you buy it at this price, do you wait for a lower price, what do you do when it looks like the world might end - those things are harder. Knowing whether you stand there, buy more, or whether something has legitimately gone wrong and you need to sell, those are harder things. That you learn with experience, by having the right psychological makeup.

When a Wall Street analyst or broker expresses optimism, investors must take it with a grain of salt.

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.

While no one wishes to incur losses, you couldn't prove it from an examination of the behavior of most investors and speculators. The speculative urge that lies within most of us is strong; the prospect of a free lunch can be compelling, especially when others have already seemingly partaken. It can be hard to concentrate on potential losses while others are greedily reaching for gains and your broker is on the phone offering shares in the latest "hot" initial public offering. Yet the avoidance of loss is the surest way to ensure a profitable outcome.

Value investors have to be patient and disciplined, but what I really think is you need not to be greedy. If you're greedy and you leverage, you blow up. Almost every financial blow up is because of leverage.

Value investors will not invest in businesses that they cannot readily understand or ones they find excessively risky. Hence few value investors will own the shares of technology companies. Many also shun commercial banks, which they consider to have unanalyzable assets, as well as property and casualty insurance companies, which have both unanalyzable assets and liabilities.

When all feels calm and prices surge, the markets may feel safe; but, in fact, they are dangerous because few investors are focusing on risk.