This bear market probably has you asking yourself a lot of questions about your past investment decisions and how to prepare your portfolio for the future. But your biggest question may be a pretty simple one: Should I really buy stocks right now?

That's because it can be a little scary to see broad market indexes and shares of strong companies falling by double-digit percentages. True, those declines have left many companies trading at dirt-cheap levels. But the natural concern is that they may drop even further.

At times like these, it's a good idea to listen to the wisdom of great investors who have successfully navigated many market downturns. In particular, I recommend heeding 16 key words from billionaire investor Warren Buffett.

Buffett's track record

Buffett is known for keeping a cool head during even the worst of times. And that's helped him to deliver superior investing performances. With Buffett at the helm, Berkshire Hathaway has reported compound annual gains of 20% over more than 55 years. That compares to the average annual gain of 10% for the S&P 500. It's clear Buffett's strategy works in good times and in bad.

Back in 2009, during a speech at Columbia University, Buffett offered this piece of advice that can help investors decide what to do during these difficult times:

Don't pass up something that's attractive today because you think you will find something better tomorrow.

This quote can guide us in many ways. But the one I'm thinking of right now has to do with valuation. Today, many great companies trade at attractive valuations. But we might be tempted to hold off from buying them thinking their prices could fall even further. That might happen.

Buffett, though, warns us that we shouldn't wait for that hypothetical better moment. It's impossible to accurately and consistently time the market. You might get the stock you want to buy at a cheaper price. Or it might rebound while you're waiting, and you'll end up paying more for it. But if you hold on for the long term, even the benefits you might have gotten from waiting might not matter much to your returns.

It's better to grab an opportunity right away. If a stock is attractive today, add it to your portfolio and hold on for the long term.

Buying Coca-Cola after a crash

Buffett's strategy around the purchase of one of his favorite stocks is a good example of seizing opportunity. He initially bought shares of Coca-Cola (KO -0.61%) after the 1987 market crash. Since that time, the stock has climbed more than 3,000%. And he has added to Berkshire Hathaway's position in the beverage giant at other points since that original purchase.

The stock rose and fell many times from the late 1980s through today -- but even purchases at the cyclical high points on its chart would have resulted in impressive long-term gains.

KO Chart

KO data by YCharts

Of course, this won't happen with every stock. Before you make any investment, it's important to study the company's track record, its earnings, its prospects, financial strength, and valuation -- as well as industry-specific factors like brand strength or its relationships with its customers.

During difficult economic times and market downturns, be on the lookout for companies that have what it takes to weather storms. Right now, there are plenty of examples in one of the hardest-hit industries -- consumer goods.

Amazon (AMZN -0.68%) shares have slid 37% this year. Higher inflation means rising costs for Amazon -- and consumers with less buying power. Still, the company's a leader in two growth businesses, and its long-term prospects are bright.

Home Depot's (HD 1.07%) share price has dropped 28%. That decline came even as the world's biggest home improvement retailer reported record quarterly revenue and earnings in the most recent quarter. Both of these stocks are trading at bargain valuations in relation to their sales. And revenues at both continue to climb.

So, when bear markets happen, don't flee the market. Instead, consider the words of experts like Buffett and seize the day.