In an attempt to integrate theorizing on action shielding with affective influences on effort-related cardiovascular response, an experiment with N = 115 university students (90% women) tested whether working on a task by personal choice vs. external assignment moderates the effect of happy vs. sad background music on effort-related cardiovascular response during task performance. We predicted strong action shielding and low receptivity for incidental affective influences when participants could ostensibly choose the task to be performed. Given the difficult nature of the task, we thus expected strong effort-related cardiovascular responses due to high commitment when the task was chosen. By contrast, for assigned-task participants, we expected high receptivity for incidental affective influences and thus predicted strong cardiovascular reactivity when they were exposed to happy music but low responses due to disengagement when they were exposed to sad music. Effects on responses of cardiac pre-ejection period, systolic blood pressure, and heart rate confirmed our effort-related predictions. Apparently, personal choice of a task can immunize individuals against incidental affective influences on resource mobilization.