What Should You Do With Your Investments if the Stock Market Crashes? This 1 Move Is Key.

The S&P 500 index (SNPINDEX: ^GSPC) is up about 12% in 2026, and the Vanguard S&P 500 ETF (NYSEMKT: VOO) has delivered annualized returns of about 15.3% for the past 10 years.

But despite this long winning streak on Wall Street, many investors are feeling anxious. Whether that anxiety is focused on artificial intelligence, higher bond yields, high stock valuations, stubborn inflation, or just a vague sense that what goes up must come down, some are seeing evidence all around that we're about to have a stock market crash.

Here's the thing: No one knows if the stock market will go up or down on any given day. The future is unknowable. But we do know that there's one big move that every investor should try to make during a bear market.

That move is: Hold on. Bear markets feel like a roller coaster, so stick to your seat (and your stocks).

Let's look at why bear markets can test the will of buy-and-hold investors -- and why most people are better off staying invested for the long haul, even if there are some big declines in the short term.

Image source: Getty Images.

Don't time the market -- stay invested

When stock prices are plummeting, many people start to wonder if they should try to sell stocks at just the right time (before share prices drop even more), or hold off on buying more stocks until just the right time (when the market hits the bottom).

This is an understandable urge, but it's misguided. Trying to wait until just the right time to buy or sell stocks is called timing the market. And unfortunately, it just doesn't work.

What if you sell stocks on a day when your shares are down 10%, and then they drop another 5%? Would you really swoop in and buy back those shares? Or would the further 5% price decline make it feel too scary?

And then, what if you wait too long to buy back into the stock market, and the market bounces back faster than you can invest? That's the really big risk of timing the market -- if you try to avoid today's stock market losses, you might end up losing even more money by missing out on future stock market gains.

The cost of timing the market: 40% lower annualized returns in 20 years

Not every day in the stock market is equally valuable to your portfolio. Just a few "good" days in the stock market make up a surprisingly large share of overall returns. Schwab recently did a study of 20 years of historical S&P 500 returns, from 2005-2024. It found that investors who missed the 10 best-performing days in the S&P 500 during those 20 years received annualized returns that were about 40% lower than the S&P 500 average return.

During those 20 years, the S&P 500 compounded at 10.3% annually. Missing out on the 10 best days of stock market performance -- about one day every two years -- would have given investors an annualized return of only 6.1%.

This is the cost of timing the market. It might feel safe and smart to move money in and out of stocks when the news is full of bad headlines and red arrows pointing down. But stock market history shows that no one is skillful enough (or lucky enough) to know "the right time" to buy stocks.

The best bear market move for most investors: Keep buying a diversified portfolio of stocks as often as you can, and then hold on to those stocks for the long term (which might mean five years, 10 years, 20 years, or more.) That's a simple, time-tested strategy to earn significant returns.

Ben Gran has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Vanguard S&P 500 ETF. The Motley Fool has a disclosure policy.