“No regrets” is a fun slogan for a T-shirt or tattoo. But it certainly wasn’t the motto of How to Win Friends and Influence People author Dale Carnegie. In fact, his approach was the exact opposite.

Carnegie–the granddaddy of self-improvement advice–forced himself to minutely note down his every slip-up, embarrassment, and dunderheaded mistake and file them in a folder he colorfully titled, “Damned Fool Things I Have Done.”

That was decades ago, but modern psychology research confirms Carnegie was on to something. Facing your regrets in this way may be brutal on your ego, but science shows it is also a brilliant way to learn from your mistakes and build a life that you’re truly proud of. Even Dale Carnegie had plenty of regrets

Carnegie’s biography details his mania for keeping his “damn fool” folders. “I put in that folder, month after month, written records of the damned fool things I have been guilty of,” Carnegie explains. “I sometimes dictate these memos to my secretary, but sometimes they are so personal, so stupid, that I am ashamed to dictate them, so I write them in longhand.”

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A blog called “The Art of Manliness” recently dug up some entries from those folders. Many will strike the average entrepreneur as quite familiar. Plenty of Carnegie’s missteps are the kind of everyday awkwardness or thoughtlessness most of us have experienced, but try to forget as quickly as possible. Examples include:

“Wasted ten minutes in an unnecessary harangue with the phone company about their shortcomings.”

“H.P. Gant made an extraordinary success as toastmaster tonight. I should have complimented him highly, but I was so absorbed in myself that I neglected to say any words of appreciation.”

“While teaching the 5-7 PM class, that ‘all Tammany politicians are crooks,’ or something nearly that. Joseph Davern, an ardent Catholic, took a feeling of exception to it. It was just at the time that religious controversy regarding Al Smith’s religion was developing. Davern made a most excellent speech on tolerance, decrying the fact that I should make such an unguarded and unfounded accusation. I apologized.”

This is a healthy reminder that even the most seemingly put-together people flub their lines and lose their tempers just like the rest of us. But according to a boatload of modern science, there is also a deeper lesson to Carnegie’s “Damned Fool Things I Have Done” folder. Your regrets are a goldmine of insight

Regrets, psychological research shows, are actually a rich source of learning and motivation. And all you have to do to claim this motherlode of insight is be brave enough to follow Carnegie’s example and actually mine your worst moments for lessons.

Many of us are naturally inclined to go the other way, pushing thoughts of our most embarrassing or ill-judged moments out of our minds as soon as possible. We try to forget roads not taken that may have led us somewhere better in life. But recent research out of Cornell University and the New School found that strategy neither takes the sting out of the regret nor teaches us anything.

Regrets you refuse to face just simmer endlessly beneath the surface, draining your life of satisfaction and joy perpetually. Instead of boxing up your feelings of regret, these studies suggest forcing yourself to carefully examine them, Dale Carnegie-style. This often leads to ideas on how to create a life that’s more in line with your true values and aspirations.

For example, Shai Davidai, one of the psychologists behind this research, always regretted not accepting a job at a ski resort earlier in his life because it conflicted with an exam he was due to take. In part motivated by his own findings, he faced his nagging regret about choosing duty over adventure and vowed to take one adventurous trip a year and be more intentional about exploring his city on the weekends. Experts agree: you’ll be happier if you face your regrets

Contemporary experts from a variety of disciplines have intuited the same insight. Best-selling author Dan Pink has written a whole book on the power of regrets to teach you about yourself, while New Yorker writer Kathryn Schulz gave a much-watched TED Talk on embracing your regrets.

“If you want to be fully functional, and fully human, and fully humane, I think you need to learn to live not without regret, but with it,” she argues.

In a business context, leadership expert Manfred Kets de Vries teaches that regret “forces us to engage in a retrospective analysis to understand why we thought or acted the way we did. Such a review may help us see specific patterns or behaviors that have made us who we are, but also kept us from leading a different life.”

Another best-selling author and popular commentator on technology and productivity, Cal Newport, apparently advocates facing your disappointments head-on too. He advised one mentee to regularly carve out time to reflect on uncomfortable questions like, “I tried X — why didn’t it work?” and “Why am I not as successful as I would like?”

All of which is a long-winded way of saying Dale Carnegie’s “Damn Fool Things I Have Done” folder isn’t a quaint eccentricity. You might want to update Carnegie’s terminology (or not — I personally like Carnegie’s blunt file label) or swap a Google Drive for paper folders. But the idea of systematically collecting your regrets has aged incredibly well.

A “no regrets” philosophy ends with repression, stagnation, and niggling doubts. Facing your biggest f**k ups is unpleasant upfront, but leads to greater personal growth in the end.