What gives this observation its teeth is the recognition that impossibility isn't a fixed condition but rather a *psychological state*—the feeling dissolves the moment we cross the finish line, yet it felt utterly real beforehand. Mandela, who spent twenty-seven years in prison before helping dismantle apartheid, understood that our greatest barrier isn't circumstance but the mind's tendency to mistake difficulty for impossibility. When a student finally grasps a concept that seemed incomprehensible weeks earlier, or when someone leaves a relationship they'd convinced themselves they were trapped in, they discover what Mandela knew: the boundary between "can't" and "can" is far more permeable than we believe while standing on the wrong side of it. The quote's quiet power lies in suggesting that if you've already done something hard, you've already proven that your sense of impossibility cannot be trusted—a lesson worth remembering the next time you face something new.