Back on track

You might decide to keep your portfolio half in stocks and half in bonds. But over time, as various investments grow, you might end up with a 60/40 mix. That's why many financial planners "rebalance" the portfolio. When you rebalance, you shift assets back to the original proportions that you selected in your plan.

You might be able to rebalance from your own computer, says Berg. "Just go online to whoever is your 401(k) provider to see if this is available," he says.

So how often should you rebalance? That depends on your planner. Some advisers recommend every three months or even every time you reinvest money. Others have found that once a year is fine for most investors.

"At our firm, we find that a once a year checkup is sufficient," says Berg. In that period, "they haven't gotten too off track," he says. "You see 1 percent to 2 percent variance in a year, even in a volatile year."

"The important thing is that you annually rebalance the account," says Miller. "But you're also coming back saying, 'Am I comfortable with my risk tolerance?'"

Some planners set an allocation spectrum for their clients.

"You have a target asset allocation, and a minimum, and a maximum -- a range," says Swedroe.

Beware of playing or reacting to the market or the current economic climate, Miller says. Investors who try to play the ups and downs of the market "sabotage themselves," she says. "You really have to put asset allocation, diversification and rebalancing together."

Asset allocation can help investors weather those financial storms.

"There's nothing different about these times than any other times," says Swedroe. It's just that "the risk is showing up now."

But, he says, "If you build a plan for 30 to 50 years, there will be times like these showing up."