The real wisdom here isn't that persistence pays off—that's the greeting-card version. Thatcher is pointing to something harder: that victory itself can be fragile, that winning doesn't end the struggle but merely completes one round. A reformed alcoholic who stays sober for five years hasn't "won" drinking once and for all; they're fighting the same battle daily, and understanding this keeps them honest. The quote asks us to abandon the fantasy of permanent triumph and instead build our strength for the long, repetitive work ahead.