The radical claim here isn't merely that positive thinking yields positive results—it's that your thoughts *constitute* you rather than simply influence you. You aren't a fixed self that thinks; you're the accumulated product of thinking itself, which means the self is endlessly revisable through attention. A person who spends five years mentally rehearsing resentment toward a colleague doesn't just become bitter; they literally reconstruct their neural pathways, their reflexive emotional responses, their face in the mirror. This explains why regret alone changes nothing, but redirecting thought—genuinely, repeatedly—can remake a person from the inside out.