As a novice investor in 2007, one of the most often touted pieces of investing advice I heard was to “take some of your winnings off the table.” The argument went that if a stock has gone up significantly, you should sell enough stock to cover your original investment, so you’ll be playing with “house money.”
I have since learned that there’s no such thing as “house money” in investing — it’s all mine. I also came to understand that there’s an important distinction between investing and gambling, and while I am an avid investor, I try not to gamble with my future.
https://www.fool.com/investing/2018/08/17/my-most-expensive-investing-mistake-and-what-you-c.aspx