Background: Understanding teachers' experiences throughout the school closures and reopenings that have characterized large periods of the COVID-19 pandemic provides us with unique insights into what it means to be a teacher during a global public health crisis. Aim and Method: To investigate teachers' narratives of their experiences, we conducted 95 semi-structured interviews with 24 teachers in England across four time points between April and November 2020. We used a longitudinal qualitative trajectory analysis of participants' stories of their high-, low- and turning-points. Results: We derived four themes that were evident at each time point and developed over time. The themes were: (1) "growing frustration at uncertainties caused by poor government leadership," (2) "expanding concern for pupil learning and well-being," (3) "an increasingly labour-intensive and exhausting job" and (4) "declining pleasure and pride in being a teacher." Conclusions: The findings shed light on the impact of COVID-19 on the professional identity of these teachers and we propose ways in which teachers can be supported now and in the future.