A third thing that is important is something Warren Buffett calls the circle of competence: Stay within what you know you can do and avoid things that you don’t know much about. I think when we see others succeed wildly with something, we are tempted to wade a bit beyond what we’re comfortable with. And that typically doesn’t work out very well.

Buffett’s circle of competence comment is the source of the name of this blog. More important than a big circle of competence is staying within yours.

Interview with Michael Mauboussin: The Role of Luck and Skill in Investing