Why does Ross Edgley keep choosing swims that could kill him? The ultra-endurance athlete, who swam around Great Britain and the Yukon, breaks down the motivation spokes that drive persistence, from fear of shame to love for his son. Huberman joins him to test a new framework of resilience. Mice that consistently win fights can be made to lose by silencing a prefrontal cortex region, and losers can be made to win by boosting it.