Investors aren’t thrilled about President Donald Trump’s new tariff policy.

The S&P 500 sold off sharply on Thursday and Friday following the President’s announcement of a baseline 10% tariff on all trading partners and duties as high as 50% on countries with which the U.S. has a trade deficit.

The selloff continued at open on Monday, with the index falling another 4% in early trading and even flirting with bear market territory — defined as a 20% decline from recent highs. Following some volatile trading, as of the early afternoon on Monday the S&P 500 had fallen about 19% from its record high in February.

Investors fear things could get worse. Other countries, including China, are already installing retaliatory tariffs — a sign that Trump’s move may have been the opening salvo in a trade war that could significantly slow the global economy. On the home front, concerns persist that the sweeping tariffs could reignite inflation and put U.S. consumers in a crunch.

Plus, market historians say U.S. tariff levels are now set to exceed those of the Smoot-Hawley Tariff Act of 1930, an economic policy often cited by economists as a contributing factor to the Great Depression.

When you’re living through them, moments of economic turmoil can feel catastrophic. But it can be worth taking a moment to put things in perspective. The following chart, which depicts the historical growth of the broad U.S. stock market, includes the five worst bear markets since 1928, including the Great Depression, a period during which stocks plummeted by 83%.

The further back you go, the less severe the bear markets look. The Great Depression hardly even registers. The historical upward trajectory of the stock market has reduced the greatest economic calamity in U.S. history into a blip.

And if market history tells us anything, it’s that downturns are often the best times to buy, assuming you have the resources to continue regularly investing.

“Everybody wants an entry point. But those entry points come when your asset value is down 20%,” says Scott Helfstein, head of investment strategy at Global X. “That’s when you get to buy assets at a discount.”

Helfstein and other investing pros acknowledge that it doesn’t feel good to buy when the market is struggling. No one wants to commit a significant amount of money to an asset that might be on its way further down.

“Psychologically, that’s very, very hard for people to do, because they’re experiencing losses,” Helfstein says. “They’re looking at any dry powder they may have and saying to themselves, ‘Well, why do I want to put that at risk for further draw down?'”

The answer, historically, has been that markets bounce back and create new highs. And it tends to happen quicker than you might think.

Between December 1945 and March of this year, the S&P 500 experienced a correction — a drawdown between 10% and 19.9% — 24 times, with an average decline of 14%, according to data from investing research firm CFRA. From the index’s lowest level, it took an average of four months to get back to break even.

In the 14 instances of bear markets over that period, the decline from peak to trough lasted an average of 13 months before things started turning around. Once they did, a new peak was found in 23 months, on average.

Based on historical averages, investors could be in for as much as a few years of pain. That’s bad news for those relying at least in part on their stock portfolio to realize short-term goals, such as buying a home or funding an imminent retirement.

For many younger investors, though, long-term goals such as retirement are decades away. That stretch of time can make a few down years look like relatively small potatoes. If you buy consistently through downturns, you effectively lower the price you pay for your investments, which will boost your returns over the long term.

By the time you retire, investing pros say, the worst markets you’ve lived through will likely look like the short-term setbacks they are in the graph above.

“When you have a long time horizon, you should absolutely be looking at these as buying opportunities,” Helfstein says.

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