The aim of this article is to propose an interpretation of pathological worry and rumination based on the control-mastery theory (CMT), an integrative, relational cognitive-dynamic theory of mental functioning, psychopathology, and psychotherapy process developed by Joseph Weiss and empirically verified by Weiss, Harold Sampson, and the San Francisco Psychotherapy Research Group over the last 50 years. In the first part of this article, we will introduce the basic concepts of CMT and how this theory integrates dynamic and cognitive concepts into a relational theoretical frame. Then, we will review several definitions of pathological worry and rumination and their clinical features and consequences. We will differentiate these processes from the normal reflection processes aimed at solving problems and mastering traumas and will review research data supporting this differentiation. Finally, we will discuss some of the more important cognitive theoretical models for explaining pathological worry and rumination. In the last part of this article, we will describe how CMT can help understand pathological worries and ruminations and their functions. According to CMT, pathological worry and rumination are distortions of normal reflexive thinking often caused by pathogenic beliefs that support interpersonal guilt, and their unconscious aim is often self-punishment. Three clinical vignettes will help us show how CMT can help us understand and treat pathological worry and ruminations.