Unlike our animal cousins, who learn from their close calls but don’t obsess about them, we tend to keep going over worries, resentments, and self-criticism: “So many things could go wrong.” “How dare they treat me that way?” “I am such an idiot!” The thoughts and feelings we have while ruminating change the brain just as other negative experiences do. Running these loops repeatedly is like running laps in soft dirt, deepening the track each time we go around it—which makes it easier to fall into negative rumination in the future.
