High-performing adults — executives, entrepreneurs, elite athletes, and senior professionals — represent a population in which the relationship between achievement and wellbeing is systematically inverted. Empirical research documents elevated rates of burnout, depression, anxiety, and impostor syndrome in this population despite, and in some cases because of, exceptional external success. Yet positive psychology has devoted comparatively little theoretical attention to explaining why achievement fails to produce flourishing in high performers, or to identifying the structural conditions that make this failure predictable rather than anomalous. This paper proposes a theoretical framework — the paradox of insufficient success — to account for this gap. Drawing on empirical literatures in burnout research, contingent self-worth, social comparison, identity development, and attachment theory, the paper argues that high-performance suffering is not incidental but constitutive: the predictable outcome of three interlocking structural dynamics. First, compensatory motivation, in which achievement is recruited to manage developmental fracture rather than to express genuine values. Second, identity foreclosure, in which self-worth becomes fused with performance outcomes, rendering identity structurally fragile. Third, cultural amplification, in which institutional myths reinforce and intensify the first two dynamics. The paper further argues that positive psychology’s traditional orientation toward the promotion of flourishing requires supplementation by a structural account of why flourishing fails in this population — and proposes suffering-as-developmental-signal as a reframing that connects the paradox of insufficient success to positive psychology’s broader agenda.