The Willpower Instinct: How Self-Control Works, Why It Matters, and What You Can Do To Get More of It

by Kelly McGonigal

Over time, the least-fit cadet in a squadron gradually brought down the fitness levels of the other cadets. In fact, once a cadet arrived at the academy, the fitness level of the least-fit cadet in his squadron was a better predictor of his fitness performance than that cadet’s own pre-academy fitness level.