Another one that makes me want to stick a toothpick in my eye -- PetSmart ( PETM). Having always loved that company's long-term prospects, I purchased 500 shares as a 25-year old sometime around the year 2000. As was the case with WEN and DPZ, I lost patience and sold. Nothing -- not one thing -- had changed with my original conviction for buying stock in each company. Nothing. So, in these cases, I was actually a great stock picker, but just a horrible position manager. It's really quite irrational. You have a thesis. You understand that, particularly in retail, it takes some time to develop so impatience leads to anxiety and a shallow questioning of your original reasoning. You sell. You regret it. On the flip side, if you bought and held Apple ( AAPL) and Amazon.com ( AMZN) ten years ago, you did far better for yourself than if you did the same with Hewlett-Packard ( HPQ) and Cisco Systems ( CSCO). AMZN data by YCharts Over a five-year period, you would have actually lost money on HPQ and earned a relative pittance on CSCO. AMZN data by YCharts Depending on when you bought them over the last decade, you needed to reassess why you bought HPQ and CSCO to avoid losing money or subpar returns. AAPL and AMZN - a different story. I tend to focus on writing about tech and media companies these days. That's how I feel best relating to investors and the broader audience. But it's instructive, whether you can own stocks or not, to go back once in a while and reconsider the obvious. For many investors, however, the obvious only appears that way in hindsight. Follow @rocco_thestreet -- Written by Rocco Pendola in Santa Monica, Calif.