Size will hurt returns. Look at Berkshire Hathaway - the last five things Warren has done have generated returns that are splendid by historical standards, but now give him $100 billion in assets and measure outcomes across all of it, it doesn't look so good. We can only buy big positions, and the only time we can get big positions is during a horrible period of decline or stasis. That really doesn't happen very often.

With so much money riding on reported numbers, human nature is to manipulate them. And with so many doing it, you get Serpico effects, where everyone rationalizes that it's okay because everyone else is doing it. It is always thus.

The world is getting very much more competitive.

Part of that, I think, is being able to tune out folly, as distinguished from recognizing wisdom. You've got whole categories of things you just bat away so your brain isn't cluttered with them. That way, you're better able to pick up a few sensible things to do.

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.

A business model that relies on trickery is doomed to fail.

Assume life will be really tough, and then ask if you can handle it. If the answer is yes, you've won.