PALO ALTO, Calif. (CNN/Money) - There's a simple lesson for all investors in the shellacking the stock price of software maker Intuit took Friday: Sell -- or at the very least, trim -- your winners.

It's a tactic the pros use that can be easily replicated by the common folk. It'll also save you from seeing your few paper profits evaporate.

In hindsight, Intuit's (INTU: Research, Estimates) shares were an ideal candidate for a bit of a haircut. As CNN/Money's Paul La Monica detailed earlier, Intuit's shares had gained 22 percent since the company reported solid results last month.

More to the point, its valuation soared from a rich 30 times earnings to a P/E of 37, which was really rich. And so when Intuit disclosed Friday morning that the next two quarters it reports will be worse than expected, the shares quickly gave up everything they'd gained. The stock closed down 24 percent.

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It's easy to understand why many Intuit shareholders would have been reluctant to sell their stock no matter what. The maker of tax and accounting software has trounced the rest of the market for tech stocks, making it a hero among its downtrodden Nasdaq brethren. But pros understand that when a stock has had the kind of run that Intuit has, the thing to do is to sell some. Remember, the object of investing is to make money, not to admire how much of it sits in your brokerage account.

Another good example would be the recent action in gold. It's down 13 percent since February, when it had soared for months. Had you been an aggressive gold buyer in 2002 -- as many smart stock-market scaredycats were -- you would have been way up at that point. Good time to have sold some? In hindsight, obviously.

Now consider the word "some." No one's suggesting you dump all your shares in a winner. Investors invest for the long haul. That's great. The idea here is to avoid being greedy. Trimming some off the top is a good way to boost your returns without giving up on the stock. It's not all or nothing. Cutting back on your winners is a good way to have it all.

Have you noticed which mega-stock hasn't participated in the huge stock run-up of the past two days? Not even a little? That's right, Cisco Systems (CSCO: Research, Estimates), yesteryear's Silicon Valley darling. Never mind 3Com's (COMS: Research, Estimates) alliance with would-be Cisco killer Huawei Technologies of China. That's interesting, but 3Com stopped frightening Cisco years ago.

The really troubling development is Cisco's acquisition of wireless router maker Linksys for $500 million. It's bad enough that Linksys is in a rapidly commoditizing business and that it sells to consumers, a totally new avenue for Cisco. The story's really all about profitability. Cisco achieves gross margins of about 70 percent. Margins at Linksys are about half that.

Even though it's a small deal for Cisco, it's a possible sign of panic that it would enter a market where the profitability is half of what it's used to. Hence the stalled stock.

Adam Lashinsky is a senior writer for Fortune magazine. Send e-mail to Adam at lashinskysbottomline@yahoo.com.

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