This chapter explores the critical role of data-driven decision-making in optimizing human performance in the human weapon system (HWS). The authors outline the distinctions between data, metrics, and key performance indicators (KPIs), emphasizing their hierarchy and application in evaluating and improving performance. The process described by the authors is a unique, field-tested process for selecting meaningful KPIs tailored to the unique demands of HWS roles. Furthermore, this chapter examines stress’s acute and chronic effects on the autonomic nervous system. Integrating biowearables provides meaningful insights into monitoring and managing stress, sleep, and training loads, discussed throughout this chapter. Proper KPI selection combined with proactive interventions underscores the importance of aligning metrics with organizational and operational goals to enhance resilience, combat regeneration, and long-term health in high-stakes environments.