Our mental health is influenced by the emotional states we experience. Emotional states, in turn, depend on external experiences and internal processes that determine the form and persistence of emotional states. Emotion regulation strategies aim to alter emotional states and are an important element of evidence-based, effective psychotherapeutic interventions. However, the mechanisms by which emotion regulation works remain incompletely understood. Here, we combine experimental induction of momentary emotions with formal dynamical system theory to study how emotion regulation strategies influence emotion dynamics. Participants (N=109) repeatedly reported their multidimensional emotional state while watching brief validated emotional video clips. Participants were then randomized to either an emotion regulation (distancing) or control intervention before watching further video clips. Dynamical and controllability features were inferred from participants' emotion ratings using a Kalman Filter, which captures how emotions evolve, interact, and are affected by external inputs. First, we showed that the Kalman filter provided an adequate account of the data. Emotions were maintained across stimuli, interacted and were richly influenced by emotional stimuli. Second, distancing had a dual effect: It reduced the (external) controllability of emotional states both by stabilizing specific emotional dynamics and by reducing the driving force external emotional stimuli exerted. These results provide a novel, quantitative approach to characterizing how emotions are controlled and how a distancing intervention alters emotional experience. The quantitative characterization of specific psychotherapeutic interventions may help better understand and target interventions.