This quote might help: “Some people automatically sell the “winners”—stocks that go up—and hold on to their “losers”—stocks that go down—which is about as sensible as pulling out the flowers and watering the weeds. Others automatically sell their losers and hold on to their winners, which doesn’t work out much better. Both strategies fail because they’re tied to the current movement of the stock price as an indicator of the company’s fundamental value.” - Peter Lynch