Traded good for bad

My dumbest investment was selling 1,000 shares of Shopify at $180 in order to buy shares of a different company at $17. Well, the Shopify shares continued to climb, and the other company headed south. I learned to stop chasing big gains. Focus on the big picture instead, and invest for the long term. — G.B., online

The Fool responds: Many investors end up regretting having sold great-performing stocks too soon. Shares of Shopify, a company that helps other companies set up and run online stores, were recently trading around $1,030, so your investment would have more than quintupled in value if you hadn’t sold when you did.

Selling the shares is clearly regrettable in hindsight, but think back to when you sold. Did you have confidence in the company and think its shares would keep rising? Or did you think they were overvalued? It can make sense to sell out of a stock that you’ve studied and that you think is considerably overvalued, especially if you have found a different stock that’s seemingly quite undervalued.

Note that some stocks that grow quickly over many years can always look overvalued. Amazon, for example, has often seemed too richly priced — but then, despite some volatility, it routinely keeps hitting new highs. If you’re not sure what you should do, you might just compromise and sell part of your position.