This is where stop losses come in. Granted, setting stop losses properly takes some work up front, and it isn't always easy to get the balance right. If you set your stops too wide, you are subject to heavy losses. Yet setting your stops too narrow will get you whipsawed out of positions you should have kept. Sure, you can always "buy it back later," but that means eating the spread and the commission costs. Even worse, the price may get away from you, causing you to miss the opportunity altogether. This means lost research time and fewer options for the portfolio. And most of us cannot afford to spend our time and research dollars on ideas that we don't execute correctly.