Affective (emotional) responses contribute to student engagement and, ultimately, to the decision to persist or withdraw from Computer Science as a discipline of study. We investigate affective response as a factor contributing to engagement and professional identity formation during the university-to-work transition, as supported during a senior capstone project experience. By conducting qualitative interviews and focusing on student discussion of their emotional responses during the capstone project, we note three specific ways in which affective responses contribute to the student experience. First, students are receptive to the affective responses of project sponsors during project pitching and later evaluation. Second, student affective responses are present throughout the capstone project experience, and vary widely over the life of the project. Third, student affective responses provide an indication of their engagement and investment in the projects, and are linked to real-world impact of project outcomes. This paper presents a theoretical background for focusing on affective responses in the educational space, as contributing to engagement and professional identity formation. We conclude with suggestions for how these findings might inform educational development across the CS discipline.