Understanding of the exact trajectories of mood improvements during mindfulness practice helps to optimize mindfulness-based interventions. The Mindfulness-to-Meaning model expects mood improvements to be linear, incremental, and cumulative. Our findings align with this expectation. We used multilevel growth curve models to analyze daily changes in positive mood reported by 190 Polish participants during 42 days of a mobile-app-supported, mindfulness-based intervention. The daily positive mood increased among 83.68% of participants. Participants who started the training reported worse mood improved more and faster than participants with better mood at the baseline. Dispositional mindfulness and narcissism – individual difference variables associated with high vs. low emotion regulation ability, respectively – were not associated with mood improvement trajectories. A small group of participants (16.32%) showed a steady decline in positive mood during the intervention. The results underscore the importance of a more comprehensive understanding of individual variability in benefiting from mindfulness-based interventions
