Distress—a prolonged manifestation of stress characterised by negative emotionality and perseverative negative thinking (PNT)—represents a significant public health burden. One way to view distress is as a failure of self-regulation strategies. Given the influence of internally generated processes (e.g., negative emotionality, PNT) in distress, a more sophisticated understanding of emotional functioning is required to conceptualise distress conditions. Grounded in principles of affective science and functional analysis, we argue that distress conditions are best understood by a failure of emotion generative and regulation processes that occur at different points along the unfolding of an emotional moment, including motivational mechanisms, regulatory mechanisms, and behavioural consequences. This chapter reviews (1) self-regulatory and functional perspectives on distress; (2) how the emotion regulation therapy (ERT) model can help elucidate pathways through which normative emotional responses go awry and become dysfunctional, leading to excessive emotionality and PNT; and (3) empirical support for the ERT model and its functional progressions.