A review of The Marshmallow Test by Walter Mischel. A a version of this review was published in the Wall Street Journal on September 19, 2014.

When video of Adm. William H. McRaven’s 2014 commencement address at the University of Texas at Austin was posted online, the speech went viral. Millions of viewers will remember the core message summed up in his memorable line: “If you want to change the world, start off by making your bed.”

The Navy SEAL veteran recalled that “if you make your bed every morning you will have accomplished the first task of the day. It will give you a small sense of pride and it will encourage you to do another task and another and another. By the end of the day, that one task completed will have turned into many tasks completed. Making your bed will also reinforce the fact that little things in life matter. If you can’t do the little things right, you will never do the big things right. And, if by chance you have a miserable day, you will come home to a bed that is made—that you made—and a made bed gives you encouragement that tomorrow will be better.”

Adm. McRaven’s “life lessons” in his speech are, in fact, variations on a theme examined by the legendary psychologist Walter Mischel in “The Marshmallow Test”; the key to being a successful Navy SEAL—or anything else in life—is summed up in the book’s subtitle, “Mastering Self-Control.” This fast-paced and engaging work is part memoir (Mr. Mischel recounts how he quit his three-pack-a-day smoking habit), part science book (the extensive research on self-control is artfully summarized) and part self-help tome (a chapter provides tips for increasing your willpower).

Mr. Mischel begins by describing how, in the late 1960s, he and his colleagues devised a straightforward experiment to measure self-control at the Bing Nursery School at Stanford University. In its simplest form, children between the ages of 4 and 6 were given a choice between one marshmallow now or two marshmallows if they waited 15 minutes. Some kids ate the marshmallow right away, but most would engage in unintentionally hilarious attempts to overcome temptation.

To resist the tempting treat, kids looked away, squirmed, sang or simply pretended to take a bite.

They averted their gaze, covered their eyes, squirmed in their seats or sang to themselves. They made grimacing faces, tugged at their ponytails, picked up the marshmallow and pretended to take a bite. They sniffed it, pushed it away from them, covered it up. If paired with a partner, they engaged in dialogue about how they could work together to reach the goal of doubling their pleasure. (There are numerous “marshmallow test” videos on YouTube.) About a third of the original subjects, the researchers reported, deferred gratification long enough to get the second treat.

I first learned of this research in a psychology graduate program in the 1970s, shortly after the original papers were published. At that time, the work was characterized as a study of “delay of gratification,” and there was not much fanfare surrounding the experiments. All that changed in 2006, when Mr. Mischel published a new paper in the prestigious journal Psychological Science. The researchers had done a follow-up study with the students they had tested 40 years before, examining the sort of adults they had grown into. They found that the children who were able to delay gratification had higher SAT scores entering college, higher grade-point averages at the end of college and made more money after college. Perhaps not surprisingly, they also tended to have a lower body-mass index.

Suddenly people started paying attention. New York Times columnist David Brooks considered the implications in a piece called “Marshmallows and Public Policy.” “Sesame Street” featured Cookie Monster controlling his impulses to indulge, so that he could become a member of the Cookie Connoisseurs Club. Investment companies used the marshmallow metaphor to encourage potential clients to delay gratification and save for retirement. Some parents started buying their children T-shirts that said “Don’t Eat the Marshmallows” and “I Passed the Marshmallow Test.”

It was too much. No single variable—such as self-control—can explain success or failure. Some critics have pointed out that Mr. Mischel’s original subjects were themselves children of Stanford University professors and graduate students—not exactly a representative sample. Other scientists noted that variations in home environment could account for self-control differences: Stable homes and one-child families encourage delay of gratification, whereas in unstable homes and those with multiple siblings, if you don’t nab a marshmallow now there won’t be any left in 15 minutes.

Mr. Mischel addresses these critiques, noting that studies in nonelite schools found similar results, and he acknowledges the power of the environment to shape our ability to delay gratification. While observing that genetics plays a role, too, Mr. Mischel builds a case for how “self-control can be nurtured in children and adults, so that the prefrontal cortex can be used deliberately to activate the cool system and regulate the hot system.”

This metaphor of “hot” and “cool” systems in the brain—not dissimilar to psychologist Daniel Kahneman’s model of “fast” and “slow” thinking—is meant to convey how the brain evolved to handle different environments: “one hot to deal with immediate rewards and threats,” Mr. Mischel explains, “the other cool to deal with delayed consequences.” He describes the way they work together: “As one becomes more active, the other becomes less active. The challenge is to know when it’s best to let the hot system guide your course, and when (and how) to get the cool system to wake up.”

How do you cool your hot system? Physically distance yourself from temptation in both space and time: For example, clear your fridge of tempting treats you know you shouldn’t eat. Keep reminders around of the negative consequences of gaining weight (stretched clothes) and smoking (photographs of cancerous lungs). Get a full night’s sleep and eat a healthy diet to maintain the energy level you need—exercising willpower, researchers have found, burns a lot of actual calories. Pat yourself on the back for even the smallest triumphs of self-control (like making your bed). And don’t be afraid to enlist help. Surround yourself with friends or family members who understand or share your weaknesses, who will encourage you to resist temptation and reinforce your self-control mechanisms.

In his commencement address, Adm. McRaven explained his final life lesson with an anecdote: “In SEAL training there is a bell,” he explained. “A brass bell that hangs in the center of the compound for all the students to see. All you have to do to quit—is ring the bell. Ring the bell and you no longer have to wake up at 5 o’clock. Ring the bell and you no longer have to do the freezing cold swims. Ring the bell and you no longer have to do the runs, the obstacle course, the PT—and you no longer have to endure the hardships of training. Just ring the bell.” To ring the bell is to give up.

Interestingly, one of Mr. Mischel’s lesser-known marshmallow experiments had a similar setup, with a bell that the children could ring to call back the experimenter and save them from themselves. For the children, though, ringing the bell was not giving up but calling in the cavalry. His book is an encouraging reminder that, despite all the factors that urge us to indulge, “at the end of that causal chain, it is the individual who is the agent of the action and decides when to ring the bell.” You are ultimately in control of your self.