When do people decide to do something about problematic health behaviours? Theoretical models and pragmatic considerations suggest that people should take action when they feel bad about their progress – in other words, when they experience negative progress-related affect. However, the impact of progress-related affect on goal striving has rarely been investigated. Thomas Webb is a social psychologist, interested in self-regulation and behaviour change. Specifically, he is interested in how people achieve their goals and make changes to their behaviour.