Engaging in a behaviour that has negative physical consequences is considered to be a threat to the self because it makes the self appear inadequate and non-adaptive. This self-threat is experienced as self-evaluative emotions. The self-threat can be removed by refraining from the unhealthy behaviour. The experience of self-threat influences behaviour because it contributes to expectations about the occurrence of self-evaluative emotions in the case of behaviour change. The results of Study 1, conducted among 503 smokers, showed that self-evaluative emotions were the central predictor of quitting activity during a 7-month period, among measures related to the negative consequences of smoking. The results of Study 2, conducted among 409 smokers, showed that expectations about the self-evaluative emotions that follow quitting smoking predicted quitting activity during a 9-month period and that these expectations partly mediated the relation between self-evaluative emotions and quitting. The results of Study 3, conducted among 255 smokers, showed that information on the negative outcomes of smoking led to quitting activity only when there was room to change self-evaluative outcome expectations. In addition, increases in these expectations predicted quitting activity during a 6-month period. The results suggest that negative self-evaluative emotions are a central motive to change unhealthy behaviour and that self-evaluative outcome expectations govern the behaviour change. The results can be understood within Steele's (1999) Self-affirmation theory.