1. Your beliefs influence your behavior.
One of the most basic ways that beliefs can shape reality is through their influence on behavior—no quantum physics needed. For example, if you believe that you’re capable, competent, and deserving of your dream job, you’re probably more likely to notice and seek out opportunities that could help you get there. You’re also more likely to perform well in an interview. Contrary to the common assumption that overconfidence can backfire, research suggests that it may actually be beneficial: Overconfident people (link is external) tend to appear more socially skilled and higher in social status, even when those evaluating them have access to objective information about their actual ability.
Beliefs can also influence health behaviors. Research suggests that people are more likely to engage in health-promoting behaviors like eating well and exercising if they have a greater sense of self-efficacy (link is external)—that is, if they believe that they are capable of effectively performing these behaviors. But positive thinking has its limits: Research also shows that people take better care of their health when they think negatively to some extent—when they believe that they are in fact susceptible to serious illnesses (link is external). Without awareness of the reality of the risks they face, people may lack the motivation to make healthy decisions.
Beliefs about your basic character—who you are as a person on a fundamental level—can be especially powerful. Research suggests that while guilt (feeling that you did a bad thing) can motivate self-improvement, shame (feeling like you are a bad person), tends to create a self-fulfilling prophecy (link is external), reducing hope and undermining efforts to change. By the same token, some evidence suggests that praising character as opposed to behavior is a more effective means of promoting positive behaviors. For example, in one study, children who were told that they were helpful people (link is external)for doing something generous (donating some of their marbles to poor children) later engaged in more altruistic behavior than did children whose behavior alone was praised or who did not receive praise.