I had to decide to stay upright on my surfboard. I didn't know it would help me stay upright in my life, too.

On the last day of 2014, I tried surfing for the first time. Living in Cape Town, South Africa, I often heard surf bums go on about how you “learn who you are on the board,” but on the board I realized that truism was true: Or rather, you learn both who you are and who you could yet be.

Surfing distills into a pure physical moment the usually drawn-out, intellectual, complex challenge of simultaneously accepting what life throws at you and making the best of it. At first, when I fell, I felt a desperate desire for my teacher to tell me my mistakes were normal, that I didn’t measure up poorly against the others he’d taught. It was so similar to my yearning, often, to be reassured that my mistakes don’t reflect badly on my character.

After a mixed record of successes and failures, my teacher told me that at some point I just had to “decide to stay on the board.” Amateurs imagine adventure sports are all about skills: We have to acquire strength and muscle memory before we can accomplish a sporting feat. Professionals, though, know how psychological it is. It was astonishing to experience how great a difference simply making that decision and being tenacious about it made. Where I’d been falling most of the time, I began to catch every wave. Pleasure built upon pleasure, the certainty of my ability amplifying with each new trial.

Advisers often tell us we have to be confident about our decisions. That decisions come at the end of a certainty-acquisition process and simply ratify an inner truth. But in fact, it goes the other way: Decisions create confidence. That’s what I learned on my surfboard.

Last month, the New York Times ran a beautiful piece on surfing in Sierra Leone, where Ebola still lurks darkly just onshore. Nevertheless, the Bureh Beach boys continue to surf — “as therapy,” they say. It’s been my experience of actual therapy that the therapist tries to create a contained space in which you can practice making decisions on a shorter time frame and in a less complex context than real life. But perhaps the therapy we often need is a bit more metaphorical: the chance to practice strength, joy, acceptance and resilience physically rather than intellectually, at low stakes rather than high ones.

The idea that changing the way we move our bodies can change our mental gestures is gaining some ground. A TED talk by the social psychologist Amy Cuddy suggested that mere minutes of “power poses,” simple exercises in spreading our arms and standing tall, can change how we think about ourselves and make more fundamental choices. It went viral last year, becoming one of the most-viewed TED talks ever. “Let your body tell you you’re powerful and deserving, and you become more present, enthusiastic and authentically yourself,” Cuddy said; numerous studies have indeed shown that adopting a more “open” body posture really does help subjects act in confident ways, like selecting a seat at the front of a classroom rather than in the back.