It takes a lot of work to pick winners consistently, and even more effort to keep yourself from selling them when markets sour. But that's exactly what you need to do when tumbles put your net worth at risk. Rather than looking for the exits, it can pay off to consider top stocks you don't already own -- especially top stocks in high-growth industries that usually bear the brunt of a sell-off.Make no mistake about it: When markets are dropping, it's hard to keep your fingers away from the sell button.