Maintaining psychological equilibrium within a dynamic environment is thought to be the core of human functioning. Systems-based theories of personality hypothesize that generalized processes control stability by regulating how strongly a person reacts to various situations. Research shows there are higher-order traits of general personality function (Stability) and dysfunction (general personality pathology; GPP), but whether or not they capture individual differences in reactivity is largely theoretical. We tested this hypothesis by examining how general personality functioning manifests in everyday life in two samples (Ns=205; 342 participants and 24,920; 17,761 observations) that completed an ambulatory assessment protocol. Consistent with systems-based theories, we found (1) there is a general factor reflecting reactivity across major domains of functioning, and (2) reactivity is strongly associated with Stability and GPP. Results provide insight into how people fundamentally adapt (or not) to their environments, and lays the foundation for more practical, empirical models of human functioning.