George Kelly, a prominent 1950s psychologist, helped his clients change by asking them to perform “roles” that represented new personality traits. A person who wanted to be more extroverted might, like Curt did, sign up to speak in front of people or go to bars to talk to strangers. After a few weeks, many people began to think of the roles as their real selves. “Many of Kelly’s clients reported that the new role seemed as though it had always been their real self and that it was only now that they were becoming fully aware of it,” Wiseman writes.312

Geraldine Downey, a Columbia psychologist who studies social rejection, has found that socially excluded people who want to become part of a group are better off if they assume that other people will like them. They should behave as if they are the popular kid. Going into social interactions expecting the worst—as I and many other weird kids often did—tends to be a self-fulfilling prophecy.

In one study,313 people were able to become more extroverted or conscientious over the course of four months just by listing the ways they’d like to change and what steps they would take to get there. So, someone who wanted to become more extroverted might write down, “Call Andrew and ask him to lunch on Tuesday.” After enough lunches with Andrew (and presumably with others, too), people became the extroverts they hoped to be.

Therapy can help with this process. Take neuroticism, a trait responsible for anxiety and rumination. Neuroticism tends to decline naturally with age.314 But one review of studies315 found that a month of therapy—any kind of therapy—reduced neuroticism by about half the amount you might expect to see it naturally decline over the course of your entire life. Bizarrely, even psychoanalytic therapists—who generally think personality is set in childhood—were able to help people change their personalities. The individuals’ personalities remained different for at least a year after the therapy took place.

After neuroticism, extroversion was the next most changeable personality trait, according to this research. Coincidentally, neuroticism and extroversion are the two factors that play a major role in the kind of social anxiety Curt and others experienced. Change those two elements of personality, and you can extinguish much of your self-doubt.