Chronic stress, a validated health risk factor, remains an ambiguous construct in spite of years of research. We propose that chronic stress is best understood as a series of acute stress responses, and that these responses become maladaptive when they occur frequently or are of long duration. We focus on the factors that contribute to chronic stress: whether the presence of a stressor, real or imagined, is long-lived and/or frequent (repeated activation), the degree to which the stressor is perceived as a threat even when no longer present (low or slow adaptation), and the extent to which the duration of responding is prolonged (delayed or failure to return to homeostasis). Importantly, we examine how perseverative cognitions (such as rumination and worry) contribute to chronic stress by creating and sustaining acute stress responses, largely via influencing activation, adaptation, and return to homeostasis. Finally, we discuss the implications of our stress model: that interventions can be ideographically tailored to address how an individual is experiencing chronic stress; that researchers may be better able to identify specific characteristics of chronic stress that relate most strongly to poor health; and that moderators of chronic stress may function through these contributing factors rather than via general effects on the system.