Past work has found that performing one self-control task leads to decrements on subsequent efforts at self-control. The present experiment compared two possible explanations for these decrements, one being a depletion of energy resources, and the other being self-attribution of failure from the first task. Participants performed a Stroop color-word task (an initial self-control exercise) or not, and some received success or failure feedback about their performance. Performing the self-control task led to impaired persistence on a subsequent figure-tracing task, consistent with the energy-depletion model. Success versus failure feedback had no effect, contradicting the self-attribution model.