We all have defining moments in our lives—meaningful experiences that stand out in our memory. Many of them owe a great deal to chance: A lucky encounter with someone who becomes the love of your life. A new teacher who spots a talent you didn’t know you had. A sudden loss that upends the certainties of your life. A realization that you don’t want to spend one more day in your job. These moments seem to be the product of fate or luck or maybe a higher power’s interventions. We can’t control them. But is that true? Must our defining moments just happen to us?