Berkshire Hathaway's annual shareholder meeting is one of the most-watched investor events each year. Hoping to benefit from the insights of the "Oracle of Omaha," as the company's iconic founder, Warren Buffett, is known, investors pay close attention to the musings and observations he and his top deputies share. 

This year, for example, Buffett and vice chairman Charlie Munger revealed who is in line to be CEO at the world's largest conglomerate, a topic of great interest considering both men are in their 90s. They also shared thoughts about how they may have avoided having to bail out the airlines by selling their stock ahead of action by the U.S. government, and why they sold stakes in Goldman Sachs, JPMorgan, and Wells Fargo.

More interesting, however, was an admission from Buffett that he had made a big mistake.

First, some context. Between 2016 and 2018, Buffett invested $35 billion in Apple. In May of 2016, Apple's market cap was around $500 billion. By 2018, it had grown to $900 billion. Today, it's worth more than double that number, at $2 trillion.

Eventually, Buffett's position in Apple exceeded $100 billion, not a bad return by any standard. Except, it could be higher considering Buffett sold off some of his shares last year.

"I sold some stock last year," Buffett said during the annual meeting, referring to his sale of $11 billion worth of Apple stock. "That was probably a mistake."

Technically, Buffett himself doesn't own any of the Apple shares, they're owned by Berkshire Hathaway. That's actually important, because Buffett's job is to maximize the return on the investments he makes for all of the company's shareholders. 

Buffett's admission is, in some ways, an apology to shareholders that he could have made them more money had he held his position. Neither the admission nor the apology is easy to say out loud. Buffett, however, at a moment when he knew the world was watching, said both.

Most of us know when we've made a mistake. It usually hurts. We can feel that something went wrong. 

Sure, there are times when it isn't clear right away. In Buffett's case, it would have taken some time before it became clear that he sold his company's shares in Apple too early. While it's not clear exactly when Buffett sold the shares last fall, the stock price is up roughly 20 percent since then. Obviously, no one has the benefit of hindsight when making decisions like this, or they'd be far more wealthy than Buffett.

The thing is, when we realize we've made a mistake, most of us do everything we can to make that feeling go away--to cover it up and keep anyone else from knowing about it. Sometimes, we even convince ourselves that it didn't really happen as a sort of defense mechanism.

Except, usually, when you're the most famous investor on the planet, people know. Avoiding the issue doesn't change anything.

By the way, even more revealing was Buffett's comment that Munger had tried to talk him out of it. Munger told Buffett not to sell Apple's shares, and Buffett now acknowledges he should have listened.