Live as long as you may, the first twenty years are the longest half of your life.

Southey’s aphorism plays on a paradox: no matter how long one lives, the earliest years feel disproportionately long. The “first twenty years” can seem to occupy “the longest half” because childhood and adolescence are dense with first experiences, rapid change, and heightened attention to novelty; later life, by contrast, is often structured by routine and familiarity, which can make time feel as if it passes more quickly. The line also carries a mild admonition—youth is not merely a prelude but a substantial portion of lived experience in psychological weight, shaping memory and identity. It captures a common human perception of time rather than a mathematical claim.