Prolonged stress is often followed by persistent cognitive instability, reduced mental endurance, and heightened relapse vulnerability, even after external stressors have been substantially reduced. While many models implicitly assume that recovery is roughly proportional to stress reduction, clinical and experimental observations increasingly suggest non-linear trajectories that are difficult to reconcile with level-based or depletion accounts. Here, we propose a systems-level framework in which stress-related cognitive dysfunction is conceptualized primarily as a problem of neuromodulatory regulation rather than static impairment. Focusing on the locus coeruleus-norepinephrine (LC-NE) system, we argue that prolonged stress can bias neuromodulatory dynamics toward maladaptive operating regimes characterized by elevated tonic activity and reduced phasic responsiveness. Such shifts constrain adaptive gain control and narrow the dynamic range available for context-sensitive regulation of attention, learning, and cognitive stability. This perspective offers a coherent account of multi-domain cognitive symptoms, disproportionate sensitivity to modest cognitive or emotional demands, and the persistence of dysfunction in the absence of overt neuropathology. By emphasizing timing, dynamics, and regulatory flexibility over absolute activation levels, the framework also helps clarify why symptom persistence and recovery plateaus may occur despite substantial reductions in stress exposure. Finally, we discuss methodological implications and outline how neuromodulatory dynamics may be indirectly inferred in humans.