Dynamic Assessment (DA) research in the second language (L2) field has, to date, focused almost exclusively on understanding the usefulness of forms of mediation to diagnosing learner language abilities. Largely absent from this work is examination of learner experience of engaging in DA, including the role of emotions in their orientation to the activity, sustained participation, and awareness of outcomes. We report a case study of one participant in a larger study that implemented DA in an L2 English academic writing program at a university in the U.S. The research design included an initial DA to determine areas of writing to target for individualized instruction, a five-week enrichment program informed by this diagnosis, and a follow-up DA to trace learner developmental trajectories. Following one learner through this program, we identify changes in her emotional responses to the challenges of academic writing and also the ways in which changes to these responses emerged in relation to development of her writing abilities and her awareness of strengths and difficulties in her performance. Our discussion considers the importance both of mediation that is attuned to learner emotional responsiveness as well as understanding changes to learner reflections on their abilities as outcomes of development.