Warren Buffett, nicknamed the “Oracle of Omaha,” is quite possibly the greatest investor of all time. For decades, the CEO of Berkshire Hathaway has shown his ability to read Wall Street like a book. He also has a net worth of around $150 billion, making him the fifth richest person in the world.

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However, on some of his more questionable investments, Buffett said, “In most of these cases, I was wrong in my evaluation of the economic dynamics of the company or the industry in which it operates, and we are now paying the price for my misjudgments. At other times, I stumbled in evaluating either the fidelity or the ability of incumbent managers or ones I later appointed.”

Buffett is planning on retiring as CEO of Berkshire Hathaway at the end of 2025, and despite a few hiccups here and there, he leaves behind quite an investing legacy. So if you’re trying to sharpen your investing game, you might learn a lot from Buffett’s regrets that have led to his hard-earned wisdom.

Despite his investing prowess and great business acumen, Buffett has made a few mistakes over the years. Unlike some executives who try to pass the blame to an underling, Buffett owns his errors and assumes full responsibility when he fails to deliver to shareholders. Believe it or not, Buffett has said the dumbest stock he ever bought was — drum roll, please … Berkshire Hathaway.

Buffett explained that he first invested in Berkshire Hathaway in 1962 when it was a failing textile company. He thought he would make a profit when more mills closed, so he loaded up on the stock. Later, the firm tried to chisel Buffett out of more money. A spiteful Buffett bought control of the company, fired the manager and tried to keep the textile business running for another 20 years. Buffett estimated that this vindictive move cost him $200 billion.

The investment advice here is not to let emotions factor into your financial decisions.

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In a February 2017 interview with “Squawk Box,” Buffett was asked why he’d never bought stock in Amazon. He admitted he didn’t have a good answer.

“Obviously, I should have bought it long ago, because I admired it long ago,” he said. “But I didn’t understand the power of the model as I went along. And the price always seemed to more than reflect the power of the model at that time. So, it’s one I missed big time.”

Buffett’s investments never include businesses he doesn’t understand, which is both good and bad. Backing companies blindly is not a smart move, but shying away from them completely isn’t wise either. Partnering with someone whose strengths differ from yours can help you avoid missing out on great opportunities.

Buffett’s portfolio doesn’t include Google stock, and that’s something he regrets. At the 2017 Berkshire Hathaway annual shareholders meeting, he told investors he made a mistake by not purchasing shares in the tech giant years ago when it was getting $10 per click from Geico — which is one of Berkshire Hathaway’s subsidiaries.

Buffett has shied away from tech stocks in the past because he didn’t understand their models. Still, he said he should have figured them out because he was effectively a client of the Google ad business.

What you can learn from this mistake is not to overlook investment opportunities right under your nose.

US Airways didn’t join the ranks of failed Berkshire Hathaway investments, but Buffett does regret his 1989 purchase of $358 million worth of shares in the now-consolidated airline.

The shares never appreciated, but after weathering turmoil, Forbes reported that Buffett likely got all his principal and dividends back. Buffett credited the airline’s rebound to both his and Charlie Munger’s exit from the board and the arrival of CEO Stephen Wolf. He praised the latter for saving what could’ve been a very costly investment.

The moral of the story is to research every investment before buying, so you know exactly what you’re getting into — whether you’re a beginning investor or a longtime pro.

Despite regretting the purchase of failing textile company Berkshire Hathaway in 1962, Buffett did the same thing 13 years later when he purchased Waumbec Mills — another New England textile company.

“The purchase price was a bargain based on the assets we received and the projected synergies with Berkshire’s existing textile business,” Buffett wrote in his 2014 shareholders’ letter.

Admitting his mistake, Buffett revealed his decision to buy Waumbec was a terrible one, as the mill had to be shuttered not too many years after Berkshire acquired it in 1975. The chief lesson from Buffett’s poor investment in Waumbec is to learn from your previous mistakes. When making investments, if at first you don’t succeed, move on to a new strategy.

Berkshire Hathaway owned 415 million shares of U.K.-based grocer Tesco at the end of 2012. The firm sold some stock but remained heavily invested. In 2014, the grocer overstated its profits and shares tumbled.

In his 2014 letter to shareholders, Buffett said concerns about Tesco management motivated his initial sale of stock, which resulted in a $43 million profit. Unfortunately, he didn’t move quickly on the rest.

“An attentive investor, I’m embarrassed to report, would have sold Tesco shares earlier. I made a big mistake with this investment by dawdling,” Buffett wrote. He admitted the move cost the company a $444 million after-tax loss.

The lesson from this piece of Warren Buffett’s history is to make decisions promptly.

In his 2013 letter to shareholders, Buffett explained his debacle with Energy Future Holdings. The equity owners ponied up $8 billion and borrowed even more.

“About $2 billion of the debt was purchased by Berkshire, pursuant to a decision I made without consulting with Charlie,” Buffett wrote, referring to Munger, Berkshire Hathaway’s vice chairman.

Buffett correctly predicted Energy Future Holdings would file for bankruptcy. He said Berkshire Hathaway sold its holdings for $259 million in 2013, but not before suffering an $873 million pre-tax loss.

The lesson of this Warren Buffett loss is to run big decisions by a business partner or trusted confidant before diving in headfirst.

In 2011, Warren Buffett and Berkshire Hathaway were under fire after it was revealed that David Sokol, then-chairman of several of the firm’s subsidiaries, pitched Lubrizol Corp. to Buffett as a potential takeover. The problem was that Sokol owned stock in the chemicals company.

Berkshire bought Lubrizol for roughly $9 billion, and Sokol earned a $3 million profit. Since he hadn’t disclosed his stock ownership to Buffett, this violated insider-trading rules.

Buffett didn’t realize his mistake immediately, but at the 2011 Berkshire Hathaway annual meeting, he admitted that he should have probed deeper with Sokol. The investment advice to follow here is not to be overly trusting. Ask more questions than you think are necessary, because you can’t be too careful when your reputation is on the line.

The 1998 purchase of General Reinsurance (General Re) was initially not the best move for Warren Buffett’s investment strategy. Buffett eventually turned things around, but he does have some regrets.

“After some early problems, General Re has become a fine insurance operation that we prize,” wrote Buffett in his 2016 letter to shareholders. “It was, nevertheless, a terrible mistake on my part to issue 272,200 shares of Berkshire in buying General Re, an act that increased our outstanding shares by a whopping 21.8 percent. My error caused Berkshire shareholders to give far more than they received (a practice that — despite the Biblical endorsement — is far from blessed when you are buying businesses).”

The lesson here is to fix your mistakes the right way and enjoy the rewards of success.

In his 2008 shareholders’ letter, Buffett wrote, “Without urging from Charlie or anyone else, I bought a large amount of ConocoPhillips stock when oil and gas prices were near their peak. I in no way anticipated the dramatic fall in energy prices that occurred in the last half of the year.”

Buffett spent just over $7 billion on 85 million shares of ConocoPhillips, but its market value at the time of the letter was only about $4.4 billion.

Warren Buffett’s mistake, like this one, again emphasizes the importance of consulting people you trust before making a major investment. Sometimes, getting a different perspective is the best way to see the big picture.

Jennifer Taylor contributed to the reporting for this article.

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This article originally appeared on GOBankingRates.com: 10 Investments Warren Buffett Regrets