Buying a stock is easy. It s figuring out when to sell it that s the tough part. And with the Standard & Poor's 500 index up more than 50% since March, and September waiting in the wings, it s no wonder investors are aching for an excuse to cash in their chips.

One of the reasons to lighten a position is that it has grown to become a dominant part of your overall portfolio. At 5% of my assets, a strong position shouldn t be disturbed. At 25%, however, prudence would suggest taking some steps to lighten up.

And while I don t advocate the ubiquitous rebalancing of mutual funds that has one selling performing assets to buy the laggards, we have talked extensively about the use of staggered stop-loss orders to exit greatly appreciated (and extraordinarily large) trades.

Not recommended is the trade where investors attempt to take a profit on a stock in hopes of buying it back later at a lower price, a technique I and others call the Triple Lindy. It s a move motivated by boredom and ego, not objective reality and proper technique.

As we always like to point out, the big trends take time. If you are looking for price appreciation, just as has been witnessed over the past five months, it goes without saying that most of your investment consists of holding a stock -- not trading it. And while it feels great emotionally to cash out a winner, keep in mind that when you take a profit, you stop a profit. In reality, the open winning trade is more valuable than the profit itself.

Think about how unlikely this sounds: You re going to be canny enough to correctly pick a short-term top and sell a stock just as it falls. Then you ll have the prescience to know when it bottoms for good, at which point you ll repurchase it just in time for the subsequent rally back to new highs.

Yeah and I ve got a real shot with Anne Hathaway.

This is a low probability maneuver. For one thing, it s motivated by how we think the market might act rather than how it's actually acting at the time of our analysis. If a security in which we have a position strengthens to fresh highs, what objective indication would we have that it's set for a collapse?

Also, it requires at a minimum two additional trades -- one to exit the position and another to re-establish it at a lower price. Yet it s not true that the more you trade the more you earn. In reality, trading is like surgery. The less you cut the better.

If a position grows to dominate your portfolio, staggered stop loss orders are an effective way to trim the exposure while maintaining some upside potential.

But to wake up one morning and dump a nominal trade simply because your gut is twitching and you think you can buy it back at a lower price is a long shot at best.

A Fragile Foundation

An unscientific but frightening survey from Monster Worldwide reveals that 34% of U.S. workers surveyed have one week or less of savings to cover living expenses if they lose their job. Only 20% said they had enough savings to live for six months.

We wrote last week, savings -- not spending -- is what fuels the economy forward. Most financial advisors recommend having at least six months worth of living expenses stuffed into an emergency fund, but many workers still have a way to go in order to strengthen their financial foundations.

Hands Off My Money Market

Amid the calls for increased regulation by the Securities Exchange Commission, it turns out investors in the Reserve Primary Fund (which after the collapse of Lehman Brothers in September became the first money market fund in 14 years to lose money), could end up getting as much as 99 cents on the dollar for their holdings. Even if the Fund s Lehman holdings are valued at zero, investors will receive 98.75 cents on the dollar.

So during the worst financial crisis in almost a century, the biggest hardship to befall investors in the approximately 2,000 money market funds now in operation is that one of them drops a mere 1.25%?

Hardly seems justification to enact a new slate of draconian and game-changing regulation that upsets how these otherwise useful and successful products are used.