He who keeps his cool best wins.

The line distills a pragmatic ethic Cousins often championed: emotional self-command is a decisive advantage in conflict, negotiation, and crisis. “Keeping one’s cool” implies maintaining clarity, restraint, and perspective when others are provoked into rashness. The quote suggests that victory—whether moral, strategic, or interpersonal—often goes not to the most forceful or angry participant but to the one who can think and act deliberately under pressure. It also carries an implicit critique of reactive behavior: losing composure hands control to circumstances or opponents. In this sense, the saying functions as advice about power: calmness is a form of agency.