When we own something, we value it more preciously. If we purchase any stocks than it becomes a value for us. We value more which we are holding, which is known as an endowment bias. Due to the higher value for us, we cannot able sold out or go away from our holding.

Mr. Buffett has always mentioned that not to become too much confidence.

We can see that Mr. Buffett does not get overconfidence on his own holding, but especially he mentioned that he can have poor performance for his investment. And when he felt that he could not able to manage fund then he has discontinued his partnership approach.

Mr. Buffett has made much successful investment such as see’s candy, Coca-Cola, GEICO, Nebraska Furniture Mart, etc. But he has also made a mistake to make an investment to the Salomon Brothers, US Air, and Dexter Shoes, etc.

When Berkshire had purchased Dexter shoes than they have issued shares of Berkshire for acquiring a Dexter. Dexter got bought by Berkshire for the worth of $433 million which turnouts to be a ZERO a few years later. Mr. Buffett has mentioned into his letter to shareholders that one of the biggest mistakes he had made was to acquire Dexter shoes and that is by issuing a share of Berkshire. Berkshire share was quoted at $16765 at the time of Dexter acquisition which is currently quoted at $304057, which has grown by 13% CAGR for the same period and at the same time Dexter becomes zero. Mr. Buffett had bought H.H.Brown and Lowell Shoe in the year 1991 and 1992 respectively before the acquisition of Dexter.

In the year 2000, Mr. Buffett has recognized his mistake and write of remaining accounting goodwill. The overconfidence of Mr. Buffett has hampered a huge value to the Berkshire which teaches us that we should not be overconfident for any of the trade. When we are overconfident, we cannot able to see the negative part of our trade. We have to be neutral with our holding. I always mentioned that there is not a favorite stock of mine when people asked me for my favorite holding. I would like to hold the stock until it remains within my criteria of holding. As and when it goes out of it, I put a sell order into it. If we consider any of our investment as a favorite, then we get attached towards it and we cannot able to sell it when it is going out of our criteria.

Read for more detail: Big Mistakes: The Best Investors and Their Worst Investments by Michael Batnick