Acceptance and commitment therapy (ACT) emphasizes psychological flexibility as a key set of processes that improve mental and behavioral health outcomes. Our field needs to shift from syndrome-based interventions to a process-based approach, focusing on biopsychosocial change processes relevant to each particular person, couple, or family. ACT extends its 6 core processes to encompass all well-validated change mechanisms including those at the social or biophysiological levels. It is time to challenge the hegemony of traditional psychiatric classification in favor of a personalized precision psychiatry rooted in functional analysis, idionomic statistics, and multidimensional, multilevel evolutionary science.