Objective We hypothesized that self‐knowledge and goal perseverance are mutually reinforcing because of the roles of self‐knowledge in directing goal pursuit, and of goal pursuit in structuring the self‐concept. Method To test this hypothesis, we used a daily diary design with 97 college‐aged participants for 40 days to assess whether daily self‐concept clarity and grit predict one another's next‐day levels. Data were analyzed using multilevel cross‐lagged panel modeling. Results Results indicated that daily self‐concept clarity and grit had positive and symmetric associations with each other across time, while controlling for their respective previous values. Similar crossed results were also found when testing the model using individual daily self‐concept clarity and grit items. Conclusions The results are the first to indicate the existence of reinforcing feedback loops between self‐concept clarity and grit, such that fluctuations in the clarity of self‐knowledge are associated with fluctuations in goal resolve, and vice versa. Discussion centers on the implications of these results for the functional link between mind and action and on the study's heuristic value for subsequent research.