Last week, the Nasdaq Composite hit a record high of 27,244. The S&P 500 and the Dow Jones Industrial Average were not far behind, each sitting just a few percentage points below their own recent peaks.

While the market has seen sharp pullbacks along the way, investors have enjoyed solid gains this year overall. And this year's strong showing builds on four consecutive years of gains. Since the fall of 2022, the S&P 500 has climbed nearly 115%, while the tech-heavy Nasdaq Composite has surged 160%. Much of this rally can be credited to artificial intelligence.

Despite the string of record highs, some investors are growing increasingly uneasy. A transformative new technology driving stocks sharply higher naturally brings to mind the dot-com bubble that eventually burst in the late 1990s, and that worry is understandable. If a stock market crash really is on the way, investors would do well to heed the advice of the most legendary investor of all time, Warren Buffett.

Keep investing steadily through turbulent markets

So what should investors do? Buffett's advice is simple: keep investing. Investors should "ignore the noise" and "accumulate positions in batches over the long term." If conditions turn bad, do not panic and do not sell, and never "sell stocks when bad news is everywhere."

For investors, the most fatal mistake is trying to perfectly time the market, something even Buffett and his late partner Charlie Munger could not do. In 2019, Buffett told Berkshire shareholders with his characteristic humility: "Charlie and I have no idea what the stock market will do next week or next year."

It should be noted that this advice comes with one precondition: your portfolio is made up of high-quality businesses. Do not chase hype-driven names; instead, invest in companies with durable competitive advantages, strong balance sheets, and outstanding management. As long as that precondition is met, following Buffett's advice over the long run will ultimately pay off.

What happened to investors who bought at the peak of the dot-com bubble?

Of course, it is easier said than done. Consider a set of figures: from March 24, 2000, the peak of the dot-com bubble, to today, the S&P 500 has gained more than 400%. In other words, even $1,000 invested at the worst possible moment would now be worth more than $5,000, excluding dividends, without adding another cent along the way.

Of course, the journey was far from smooth, and that investment took years just to break even, but patient investors were ultimately rewarded. The most important lesson history leaves us is exactly the idea Buffett has always championed: patient, steady investing is always the winning strategy.