The annual letter to shareholders from Berkshire Hathaway’s Chairman Warren Buffett seemed to have an underlying theme this year: Move over naysayers.

Berkshire Hathaway’s Chairman Warren Buffett trumpeted optimism of about the prospects for his insurance companies, including GEICO, which is poised to take advantage of fearful competitors. The letter was equally enthusiastic about the U.S. economy and the historical contribution of America’s immigrant population.

“Our efforts to materially increase the normalized earnings of Berkshire will be aided—as they have been throughout our managerial tenure—by America’s economic dynamism,” Buffett wrote on page 7 of the 28-page letter.

“One word sums up our country’s achievements: miraculous,” Buffett’s letter continued. “From a standing start 240 years ago—a span of time less than triple my days on Earth—Americans have combined human ingenuity, a market system, a tide of talented and ambitious immigrants, and the rule of law to deliver abundance beyond any dreams of our forefathers.”

The letter continued: “You need not be an economist to understand how well our system has worked. Just look around you. See the 75 million owner-occupied homes, the bountiful farmland, the 260 million vehicles, the hyper-productive factories, the great medical centers, the talent-filled universities, you name it—they all represent a net gain for Americans from the barren lands, primitive structures and meager output of 1776. Starting from scratch, America has amassed wealth totaling $90 trillion.”

The letter began, as past letters have, with Buffett stating that he and Vice Chair Charlie Munger expect Berkshire’s “normalized earning power per share to increase every year.”

The letter contrasts the concept normalized earnings with “actual earnings,” which may dip because of insurance mega-catastrophes or because of periodic weakness in the U.S. economy.

But the fearless will profit from their understanding of market dynamism, the letter explained.

“America’s economic achievements have led to staggering profits for stockholders. During the 20th Century, the Dow Jones Industrials advanced from 66 to 11,497, a 17,320 percent capital gain that was materially boosted by steadily increasing dividends. The trend continues: By yearend 2016, the index had advanced a further 72 percent, to 19,763.

“American business—and consequently a basket of stocks—is virtually certain to be worth far more in the years ahead. Innovation, productivity gains, entrepreneurial spirit and an abundance of capital will see to that. Ever-present naysayers may prosper by marketing their gloomy forecasts. But heaven help them if they act on the nonsense they peddle,” he wrote.

Buffett explained that many companies “will fall behind, and some will fail” but that “winnowing of that sort is a product of market dynamism.” And even when major market declines occur, affecting virtually all stocks, he advises investors to remember two things: “First, widespread fear is your friend as an investor, because it serves up bargain purchases. Second, personal fear is your enemy. It will also be unwarranted. Investors who avoid high and unnecessary costs and simply sit for an extended period with a collection of large, conservatively-financed American businesses will almost certainly do well,” he said.

Early in the letter, Buffett described the Berkshire’s recipe for success as he and Munger stay attentive to opportunities fueled by broader actions based on fear.

“Some years, the gains in underlying earning power we achieve will be minor; very occasionally, the cash register will ring loud. Charlie and I have no magic plan to add earnings except to dream big and to be prepared mentally and financially to act fast when opportunities present themselves. Every decade or so, dark clouds will fill the economic skies, and they will briefly rain gold. When downpours of that sort occur, it’s imperative that we rush outdoors carrying washtubs, not teaspoons. And that we will do,” he wrote.