Little effort has been devoted to studying the emotional experience of designers over time. Using sentiment analysis, we explore a unique corpus of designers’ written reflections on 15 different design processes. We investigate how positive and negative sentiment in the reflections change over the course of a three-month design project. Our findings indicate that change in sentiment is not attributable to time alone, but rather to different phases and methods employed by the design teams. Finally, we discuss implications and future avenues for both our results and for using sentiment analysis in HCI research.