Why fight what’s known to be decisive?
Custom is despot of mankind.

The lines juxtapose resignation with critique. “Why fight what’s known to be decisive?” suggests the futility of resisting an outcome already settled—by fate, power, or social consensus. The follow-up, “Custom is despot of mankind,” identifies one of the chief forces that makes outcomes feel “decisive”: habit and social convention. Read together, the couplet implies that people often surrender not because a situation is morally right or naturally inevitable, but because custom exerts tyrannical pressure, shaping expectations and narrowing the imaginable. The aphoristic tone turns a personal reflection into a broader social observation about conformity and the quiet coercion of tradition.