I try to get rid of people who always confidently answer questions about which they don't have any real knowledge.

To some extent, stocks are like Rembrandts. They sell based on what they've sold in the past. Bonds are much more rational. No-one thinks a bond's value will soar to the moon.

Don't do cocaine. Don't race trains. And avoid AIDS situations.

Finding a single investment that will return 20% per year for 40 years tends to happen only in dreamland. In the real world, you uncover an opportunity, and then you compare other opportunities with that. And you only invest in the most attractive opportunities. That's your opportunity cost. That's what you learn in freshman economics. The game hasn't changed at all. That's why Modern Portfolio Theory is so asinine.

Personally, I’ve gotten so that I now use a kind of two-track analysis. First, what are the factors that really govern the interests involved, rationally considered? And second, what are the subconscious influences where the brain at a subconscious level is automatically conclusions in various ways — which, by and large, are useful — but which often malfunction? One approach is rationality… And the other is to evaluate the psychological factors that cause subconscious conclusions — many of which are wrong.

Tthe first rule is that you can't really know anything if you just remember isolated facts and try and bang 'em back. If the facts don't hang together on a latticework of theory, you don't have them in a usable form.... You may have noticed students who just try to remember and pound back what is remembered. Well, they fail in school and in life.

Failure to handle psychological denial is a common way for people to go broke: you have made an enormous commitment to something. You have poured effort and money in. And the more you put in, the more that the whole consistency principle makes you think, "Now it has to work. If I put in just a little more, then it will work."