When the stock market drops, a lot of people rush to check their statements to see how much they've lost.

Not a good idea, says Manny Schiffres, executive editor of Kiplinger's Personal Finance.

"I never look at my portfolio when the market goes down a lot," Schiffres said. "I know instinctively that I've lost a lot of money, but I don't want to see the details because I might be tempted to do something stupid."

Schiffres says you should base your investments on your time horizon and your personal tolerance for risk and volatility.

"If you have a long-term horizon and a fair amount of tolerance for risk and volatility, you put your money in stocks and over the long-term stocks will deliver the highest return of any investment category," Schiffres told me.

Money you may need in the next few years should not be in the market.

"Stocks should do well over the next 15 or 20 years, but the short-term is always a big question mark," Schiffres said. "If you don't think you can handle a loss of 20, 25 or 30 percent, which would represent a garden-variety bear market, then you need to reconsider your allocation of stocks."