Should you buy, sell, or hold today? When you buy a stock, you own a slice of a business that opens its doors again tomorrow morning. And yet we shop for shares the way we shop for shirts — fixated on the sticker, terrified of the markdown. When you narrow investing down to a decision you must make today, you have implicitly agreed to be judged on a single point in time. Of course, the stock will disappoint you if you judge your performance from one buy at one single point of time.