Don't Own Too Many Names

Editor's note: As a special bonus to TheStreet.com readers, we will be running an updated version of Jim Cramer's "Twenty-Five Rules of Investing," from his latest book, Real Money: Sane Investing in an Insane World. Here's Rule 11.

In my years as a hedge fund manager, I spent three hours every day analyzing the mistakes of the day before.

That was my major task, one that I completed before anyone else came into the office, generally between 4 a.m. and 7 a.m. I would analyze every losing trade -- you don't need to analyze the winners, they take care of themselves -- and try to figure out how I could have made more money or lost less money.

I was maniacal about it. ...