If you want to improve your odds of success in life and business, then define the perimeter of your circle of competence, and operate inside. Over time, work to expand that circle but never fool yourself about where it stands today, and never be afraid to say ‘I don’t know.

Farnam Street’s Blog (fs.blog)

Sounds Simple, Go further:

• First, you have to figure out what your own aptitudes are. Understand what you know and what you are expert at.
• Second and also important is to understand what your limits are, set boundaries of what you know. And never try to go out of those boundaries.
• Then, always work inside the boundaries of knowledge you have. And slowly and gradually work to expand your boundaries and improve the depth of knowledge.
• Always never be afraid of saying “I don’t know”. Well, some people have expertise over cricket and some over chess. Both possess a huge difference, and there is no single person who can understand it all. So, it is okay if you don’t understand something and you don’t know something. You just need to accept it and say “I Don’t Know this stuff”.
• Hence, from above, you will slowly develop and expand your area of Competence, i.e. knowledge and you will start to possess more knowledge and more expertise over particular thing (s).

As given in the blog post of Farnam Street (FS) regarding “Understanding your Circle of Competence”, it says that Charlie Munger gives simple prescription:

“You have to figure out what your own aptitudes are. If you play games where other people have the aptitudes and you don’t, you’re going to lose. And that’s as close to certain as any prediction that you can make. You have to figure out where you’ve got an edge. And you’ve got to play within your own circle of competence.
               If you want to be the best tennis player in the world, you may start out trying and soon find out that it’s hopeless—that other people blow right by you. However, if you want to become the best plumbing contractor in Bemidji, that is probably doable by two-thirds of you. It takes a will. It takes the intelligence. But after a while, you’d gradually know all about the plumbing business in Bemidji and master the art. That is an attainable objective, given enough discipline. And people who could never win a chess tournament or stand in centre court in a respectable tennis tournament can rise quite high in life by slowly developing a circle of competence—which results partly from what they were born with and partly from what they slowly develop through work.”

This post is inspired by blog of Farnam Street: https://fs.blog/2013/12/circle-of-competence/