You must know the big ideas in the big disciplines, and use them routinely - all of them, not just a few. Most people are trained in one model - economics, for example - and try to solve all problems in one way. You know the old saying: to the man with a hammer, the world looks like a nail. This is a dumb way of handling problems.

Of course you want to drive that out of yourself because you want to be wise, not foolish. You also have to allow for the self-serving bias of everybody else because most people are not going to remove it all that successfully, the human condition being what it is. If you don't allow for self-serving bias in your conduct, again you're a fool.

A rough rule in life is that an organization foolish in one way in dealing with a complex system is all too likely to be foolish in another.

Learn how to ignore the examples from others when they are wrong, because few skills are more worth having.

If you have only a little capital and are young today, there are fewer opportunities than when I was young. Back then, we had just come out of a depression. Capitalism was a bad word. There had been abuses in the 1920s. A joke going around then was the guy who said, 'I bought stock for my old age and it worked - in six months, I feel like an old man!' "It's tougher for you, but that doesn't mean you won't do well - it just may take more time. But what the heck, you may live longer."

After nearly making a terrible mistake not buying See's, we've made this mistake many times. We are apparently slow learners. These opportunity costs don't show up on financial statements, but have cost us many billions.

A lot of success in life and business comes from knowing what you want to avoid: early death, a bad marriage, etc.