CNBC’s Jim Cramer opined on two of his favorite long-term holdings — Apple and Nvidia — and suggested their continued success shows that it’s worthwhile to stick with good-quality growth stocks instead of trading in and out of them.

“As Nvidia and Apple proved once again today, individual stocks are where the biggest money is,” he said. “Provided you’ve got the fortitude to stick around and you aren’t addicted to buying high and selling low – the ultimate result of endless trading.”

The indexes ripped higher on Monday to close at record highs, with the Dow Jones Industrial Average climbing 0.14%, the S&P 500 gaining 0.44% and the Nasdaq Composite adding 0.70%. Nvidia led stocks higher after the semiconductor giant revealed it would invest up to $100 billion in OpenAI as part of the data center buildout. Investors celebrated the commitment as a good sign about the future of artificial intelligence. Apple stock also saw gains on Monday after the launch of the newest line of iPhones, and analysts indicated that demand is strong.

Nvidia hit a new 52-week high to finish up 3.93%, while Apple closed up 4.31%.

Cramer suggested some investors had been feeling pessimistic about Apple, worried about the originality of the iPhone 17, how tariffs might impact sales, demand for products in China, as well as the company’s AI strategy. Cramer said it seems each of these fears “is proving to be untrue” so far, sharing his long-held belief in the uniqueness of the company and its technology. Cramer also referenced Monday comments from outgoing T-Mobile CEO Mike Sievert, who said his company’s iPhone sales are at “all-time record highs.”

Nvidia, too, had been surrounded with negative sentiments, Cramer continued, especially about its business in China as tensions between the country and the U.S. intensify. He highlighted Nvidia’s huge deal with OpenAI, saying he thinks the investment will pay off for the company.

“It’s incredibly difficult to make money in any market if all you’re going to do is trade,” Cramer said.

Nvidia declined to comment. Apple did not immediately respond to request for comment.

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Disclaimer The CNBC Investing Club holds shares of Apple and Nvidia.