OBJECTIVE: 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. DESIGN AND METHODS: Study 1 (N = 744) adopted a cross-sectional design and examined the extent to which measures of progress-related affect were correlated with intentions to take action. Study 2 (N = 409) investigated the impact of manipulating progress-related affect on intentions and behaviour in an experimental design. RESULTS: Study 1 found that, while engaging in health behaviours had the expected affective consequences (e.g. people felt bad when they were not eating healthily, exercising regularly or limiting their alcohol consumption), it was feeling good rather than bad about progress that was associated with stronger intentions. Study 2 replicated these findings. Participants induced to feel good about their eating behaviour had marginally stronger intentions to eat healthily than participants led to feel bad about their eating behaviour. CONCLUSION: The findings have implications for interventions designed to promote changes in health behaviour, as well as theoretical frameworks for understanding self-regulation.