Ultimately, what saved my mother’s life that day, and mine, too, was not fighting the current on my own. It was calling for help. The rescuers who came to our aid knew more than I did about how to handle this kind of emergency. Together, they got my mom onto the boat deck, then to solid ground and finally into the hands of expert medical staff who could care for her properly.

Most people understand the importance of asking for help in a life-or-death crisis. We know we should wave to the lifeguard during a riptide or call 911 if our house catches fire. But in our personal and professional lives, Americans are encouraged to pursue rugged individualism over interdependency. “Help from without is often enfeebling in its effects. But help from within invariably invigorates,” wrote the journalist Samuel Smiles in his 1859 book “Self-Help,” which reached a wider audience in America than in his native Britain and spawned an entire literary genre of the same name. Heroic tales of self-made Americans abound — like Thomas Edison, who tested thousands of filaments in his quest to invent the lightbulb, or Steve Jobs, a loner who transformed technology.

You might think I’d love the image of the solo striver triumphing over every challenge. After all, I’m a psychologist who wrote a book called “Grit” about the necessity of passion and perseverance for achieving long-term goals. The truth is, I hate it. Without exception, every high performer I’ve studied credits a host of supporters for their success. Research has found that a willingness to ask for help is crucial to achievement.

Consider Nicolai Tangen, the chief executive of the world’s largest wealth fund. I interviewed him recently as he was putting the finishing touches on a book he’d been writing about leadership. After praising personal qualities like energy and grit, Mr. Tangen’s book spills more ink than you can believe about his assistant, Grete Starheim. He trusts her to speak on his behalf, and he believes her when she tells him he’s wrong. “Why should such important people end up in the shadows?” Mr. Tangen asked. “Is it embarrassing to admit that you need help?”

Or consider Conan O’Brien, who told Harvard’s graduating class that he always reminds himself that he’d done nothing alone. “If I could invite everybody, alive or dead, who has contributed to my being your commencement speaker today, all of Cambridge and half of Allston would be crammed shoulder to shoulder,” he said.

Mr. Tangen and Mr. O’Brien aren’t just being modest. Studies show that knowing when to ask for help is an essential skill for children’s learning and achievement. College students who proactively seek assistance from others typically outperform those who avoid doing so. In adulthood, seeking support is an effective strategy for regulating our emotions, and having a support network is a reliable predictor of overall mental health.

Research also shows that entrepreneurs are more successful when brought together to learn from one another. That is why one venture capital firm, Y Combinator, favors funding co-founders over solo founders. It also links founders in what it calls batches, with group office hours, group dinners and an internal messaging platform for sharing knowledge. “Even if you could do all the work yourself, you need colleagues to brainstorm with, to talk you out of stupid decisions and to cheer you up when things go wrong,” Paul Graham, one of Y Combinator’s founders, once wrote.

From an early age, we suffer from what cognitive psychologists call the illusion of self-sufficiency, overlooking how much we owe our skills to other people. In one experiment, two groups of children were given a machine they’d never seen before. In the first, none managed to figure out how it worked on their own. In the second, the vast majority succeeded after seeing someone else use the machine and getting hints along the way. Still, after the experiment, 70 percent of the second group claimed they would have learned to use the machine without help.