The ability to self-regulate is key to healthy, competent functioning. The breadth of evidence supporting the importance of self-regulation is matched by such a diversity of terms, concepts, measures, and levels of analysis that the National Institutes of Health called for progress toward a unifying model. In this article, we review a lineage of conceptual models and suggest a path toward a more unifying model of self-regulation that encompasses both the dynamics of moment-to-moment changes and age-related change. Drawing from these models, we define self-regulation as the influence of the recruitment of executive processes on prepotent responses. We define these terms, locating self-regulation in the dynamic relations between prepotent responses and executive processes, and offer a theoretical-mathematical approach to testing this model.