Sustaining employees' well-being and high performance at work is a challenge for organizations in today's highly competitive environment. This study examines the dynamic reciprocal relationship between the variability in office workers' eudaimonic well-being (i.e., activity worthwhileness) and their extra-role performance. Eighty-three white-collar employees filled in a diary questionnaire twice a day, once in the morning and once in the afternoon, on four consecutive working days. The results show that eudaimonic well-being displays clear variability in a short time frame. In addition, Bayesian Multilevel Structural Equation Models (MSEMs) reveal a significant positive relationship between the levels of state eudaimonic well-being in the afternoon and the increase in the levels of state extra-role performance from that afternoon to the next morning. Moreover, the overall levels of self-reported state eudaimonic well-being across the diary measurements are significantly and positively related to the overall levels of extra-role performance assessed by the supervisor during the diary measurement. Finally, there is a significant negative relationship between the amount of intra-individual variability in state eudaimonic well-being during the week and the overall levels of self-rated state extra-role performance during the same week. These findings shed light on the dynamic nature of both the eudaimonic component of well-being and performance, highlighting the importance of eudaimonic well-being for extra-role performance and expanding the happy-productive worker thesis. The results suggest that the daily eudaimonic experience of meaning at work should complement the experience of hedonic well-being because it is an important factor in achieving better and more sustainable employee performance on a daily basis.