This special edition of Health Psychology Review provides a very impressive and welcome attempt to synthesise the evidence to date on the effectiveness of self-regulation strategies in understanding and predicting health behaviour change. In this brief commentary I reflect on three issues: (a) the importance of small treatment effects; (b) variability in how interventions are delivered; and (c) the importance of emotion in relation to self-regulation.
Keywords: Effect size; emotion; form of delivery; number needed to treat (NNT).