NEW YORK (CNN/Money) - Why is the media hell-bent on playing up the weakness in the economy? We hear that companies had their worst holiday sales in 30 years, but what people don't realize is that what really happened is many companies didn't see sales decline or lose money -- they just didn't meet their forecast, which is a different thing.

The media needs to be more positive in its reporting and get away from the idea that positive news does not sell. Nervous shoppers do not make good shoppers!

-- Joseph Lehman, Lake Forest, Calif.

I agree wholeheartedly with you that media coverage can help create a tone -- both positive and negative -- that affects how people shop for everything from clothes and gifts to houses and cars and stocks and bonds too.

And I'll also agree that the media's strong suit is not analysis and introspection. It's good at reporting facts and digging up facts, but not necessarily putting them into context or explaining to people the significance (or lack of significance) of those facts.

I think that's especially true of the financial press which, in my humble opinion, presents scads of data every day in a manner that suggests that you must know all this stuff and factor it into your investing decisions. In reality, of course, by the time the media gets the info to you, it's already been factored into investment prices.

But getting worked up about it doesn't make any sense to me. It's like complaining about the weather -- what's the point? You can't change how the financial media is going to do its job, and you can't change how individual consumers and investors will react to it.

RELATED ARTICLES In for the long haul Where did the money go? Index it and forget?

I suspect that a lot of the substanceless and feel-good reporting on dot-com and go-go tech stocks in the late '90s made these issues more attractive to individual investors that they might have been otherwise.

Similarly, I suspect that the equally excessive gloom and doom that's characterized much of the coverage of the economy and markets since the bear market and the recession has led people to be overly conservative in their investing, flocking to bonds and cash perhaps more than they ought to be.

I'm not saying the media or anyone else deserves blame for people buying overvalued tech stocks or loading up on bonds that could very well take a hit when interest rates rise. We all have to take responsibility for our own investing decisions.

But I don't think there's any doubt that the tone of the media coverage can have an effect on investors' actions, perhaps making them a bit more ebullient on the upside and a bit or pessimistic on the downside.

While you can't control that reaction, you can control something more important -- your own behavior. You can control the way you react to the tsunami of financial news we get every day and whether or not you let it affect your investing decisions.

I think it's very important that investors exert that kind of control. In the late '80s, psychologist Paul Andreassen of Harvard studied the link between the news media and investing. In one experiment, he separated people into two groups: the first bought and sold stocks based solely on recent price data, while the traded after being given the price information plus headlines that explained the price changes.

Andreassen found that when stock prices were volatile, the group that had access to the news earned less than half as much per share traded as the group that received no news. He theorized that the reason is that we tend to take news reports as predictions, and thus more likely to buy when the news is good and sell when it's not. With thousands investors reacting this way, stocks can be driven to unrealistically high or low levels.

So my advice to you and other investors isn't to ignore the news; you want to be informed about the world. But don't feel compelled to act on it, don't get swept up in the euphoria or the pessimism. Just formulate your long-term investing strategy and stock to it, regardless of how optimistic or pessimistic the media and other investors may be.

Walter Updegrave is a senior editor at MONEY Magazine and is the author of "Investing for the Financially Challenged." He can be seen regularly Monday mornings at 7:40 am on CNNfn.