The real power here isn't simply that positive thoughts breed positive outcomes—that's the greeting-card version everyone knows. Rather, Thatcher grasped something more unsettling: our habitual thoughts literally reshape our character over time, making us strangers to our former selves. A person who spends years entertaining thoughts of victimhood doesn't just feel differently; they become someone whose instincts, reflexes, and relationships reorganize around that identity. Watch a colleague who's nursed workplace resentment for a decade—you'll find their suspicion has calcified into a kind of personality, almost immune to contrary evidence.