I learned it in 1965. I used to go to the Boardroom at Merrill Lynch in Boston during my lunch hour to watch the market. I was just learning about investing at the time. Every day I would see this young man sitting there. One day I sat next to him and asked him if he worked in the area. He told me he didnâˆ™t work but was a trader. He said he went to the financial library every morning and spent his entire day watching the market. I told him I was just learning about investing and he asked me if I had learned the first lesson in investing. So I asked him what it was. He said it was learning to take a loss. I told him that I had taken losses. He then said, But have you learned to deliberately take a loss. When you make an investment that is not going the way you thought it would do you sell it and take the loss. I have never forgotten that lesson.