So, yes, self-confidence can make you try harder—but it can also work in more subtle ways. Telling runners they look relaxed makes them burn measurably less energy to sustain the same pace.12 Giving rugby players a postgame debriefing that focuses on what they did right rather than what they did wrong has effects that continue to linger a full week later, when the positive-feedback group will have higher testosterone levels and perform better in the next game.13 Even doing a good deed—or simply imagining yourself doing
