Grades are a staple of education and a gateway to future career opportunities. Yet, grading practices can (re)produce inequities and cause students to feel inadequate and unmotivated. Alternative grading practices may address these problems, but these strategies are often time intensive and impractical in larger classroom settings. In this study, we explore an easy-to-implement grading practice, in-class quiz retakes, to conceptualize how grades motivate learning and impact well-being for undergraduate students in science, technology, engineering, and mathematics (STEM). Through the lens of self-determination theory, we conducted semistructured interviews with undergraduates who experienced quiz retakes in two STEM courses. Our results revealed that retakes largely improved students' perceptions of their competence in the subject matter, autonomy in grade outcomes, feelings of relatedness to the instructors, and overall motivation to learn. The majority of students also expressed how traditional grading practices negatively impacted their motivation and well-being. In addition, a quantitative analysis revealed that quiz retakes particularly benefitted students who scored lower on their initial quizzes. We aspire for this study to prompt educators to reconsider traditional grading practices by opting for more equitable and just alternative grading approaches that motivate student learning and mitigate systemic barriers in education.