One growth stock investing cliché says “don’t fall in love with your stocks,” but you shouldn’t fall out of love with a stock so soon that you miss a winner.

Most investor sayings and clichés have at least a hint of truth. But they can still lead you to make good or bad investment decisions, depending on how you apply them. One of these clichés is very applicable to growth stock investing.

For instance, you’ll sometimes hear investors say that you shouldn’t fall in love with your stocks. This seems to make sense. You should keep an open mind about your investments, rather than falling in love with them and holding them forever, despite any adverse changes in their business or the field in which they operate. However, investors sometimes use this tidbit of advice as a justification for selling a stock that has shot up unexpectedly.

It’s easy to jump to the conclusion that unexpected strength in a stock won’t last. Brokers and cable-TV commentators may advise you to “take some money off the table” —that is, sell all or part of your market-beating stock pick. They may justify this advice by informing you that “you never go broke taking a profit”, and that you can always “buy it back on a dip”.

In fact, unexpected strength in a stock you like is a terrible reason to sell. The stock may be stronger than you expected—you may have under-estimated the growth potential or competitive advantages that led you to like it in the first place.

The danger of selling superstocks just when they’re getting started

Experienced investors can tell you that some of their best stock picks started going up out of proportion to what they expected, and kept out-performing for years. By the time the first significant “dip” or setback comes along in a stock like this, it may have tripled.

Remember, no one can predict which stocks will be average performers, which will be losers, and which ones will turn into the superstocks that wind up rising five-fold, 10-fold or more. You may avoid some temporary losses if you sell every stock you own that goes up faster than you guessed. But do that, and you will also sell any superstocks you stumble upon, often when they are just getting started. That could mean that your growth stock investing strategy never pays off as well as it might.

After all, you need a few superstocks during your investing career, to make up for the inevitable losers.

Above all, when a stock you own is unexpectedly strong, resist any impulse you feel to sell, even if you like the idea of “nailing down a profit”. Instead, look at it closely. See if you can find any good reason to sell, apart from the fact that it’s beating your expectations.

If you can’t find any good reason to sell, hang on to it. Maybe your expectations are just too low.

Have you had a major success with growth stock investing strategy? Have you ever sold a rising stock too soon, only to see it continue to soar? Please share your experience with us in the comments.

Note: This article was originally published in 2013 and has been updated.