You've heard the expressions: "He lost his nerve," "He doesn't have the stomach for it," and "No guts." As it turns out, those expressions are anatomically accurate.

The nerve that you lose when you're afraid is the vagus nerve, which runs from the belly to the brain. It transmits messages about whether the world is a safe or dangerous place. What we now know about the functioning of this nerve has direct applications to making leaders more effective and all of us happier and more courageous."

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