Objectives: A psychosocial intervention for spousal carers of people with dementia promoted emotional well-being through self-monitoring and personalized feedback, as demonstrated in a previous randomized controlled trial. The mechanism behind the intervention effects is thought to lie in increased awareness of, and thus, engagement in behaviours that elicit positive emotions (PA). This secondary analysis tests the assumption by investigating momentary data on activities, affect, and stress and explores the relevance of personalized feedback compared to self-monitoring only. Methods: The intervention was based on the experience sampling method (ESM), meaning that carers self-monitored own affect and behaviours 10 times/day over 6 weeks. The experimental group received personalized feedback on behaviours that elicit PA, while the pseudo-experimental group performed self-monitoring only. A control group was also included. ESM-data of 72 carers was analysed using multilevel mixed-effects models. Results: The experimental group reported significant increases in passive relaxation activities over the 6 weeks (B = 0.28, SE = 0.12, Z = 2.43, p <.05). Passive relaxation in this group was negatively associated with negative affect (r = –0.50, p =.01) and positively associated with activity-related stress (r = 0.52, p =.007) from baseline to post-intervention. Other activities in this or the other groups did not change significantly. Conclusion: Carer’s daily behaviours were only affected when self-monitoring was combined with personalized feedback. Changing one’s daily behaviour while caring for a person with dementia is challenging and aligned with mixed emotions. Acknowledging simultaneously positive and negative emotions, and feelings of stress is suggested to embrace the complexity of carer’s life and provide sustainable support.