The game of investing is one of making better predictions about the future than other people. How are you going to do that? One way is to limit your tries to areas of competence. If you try to predict the future of everything, you attempt too much.

Creative accounting is an absolute curse to a civilization. One could argue that double-entry bookkeeping was one of history's great advances. Using accounting for fraud and folly is a disgrace. In a democracy, it often takes a scandal to trigger reform. Enron was the most obvious example of a business culture gone wrong in a long, long time.

Using volatility as a measure of risk is nuts. Risk to us is 1) the risk of permanent loss of capital, or 2) the risk of inadequate return.

You're not going to get very far in life based on what you already know. You're going to advance in life by what you're going to learn after you leave here.

It's a rare business that doesn't have a way worse future than it has a past.

You must have the confidence to override people with more credentials than you whose cognition is impaired by incentive-caused bias or some similar psychological force that is obviously present. But there are also cases where you have to recognize that you have no wisdom to add - and that your best course is to trust some expert.

Obviously, consideration of costs is key, including opportunity costs. Of course capital isn't free. It's easy to figure out your cost of borrowing, but theorists went bonkers on the cost of equity capital. They say that if you're generating a 100% return on capital, then you shouldn't invest in something that generates an 80% return on capital. It's crazy.