In this study, data in the form of (preservice teacher) "student voices" taken from mathematical autobiographies, written at the beginning of the semester, and end-of-semester reflections, were analyzed in order to examine why preservice elementary school teachers were highly motivated in a social constructivist mathematics course in which the teacher emphasized mastery goals. The findings suggest that students entered the course with a wide variety of feelings about mathematics and their own mathematical ability. At the end of the semester, students wrote about aspects of the course that "led to their growth as a mathematical thinker and as a mathematics teacher..." Student responses were coded within themes that emerged from the data: Struggle; Construction of meaning [mathematical language; mathematical understanding]; Grouping [working in groups]; Change [self-efficacy; math self-concept]; and the Teacher's Role. These themes are described using "student voices" and within a motivation goal theory framework. The role of struggle, in relation to motivation, is discussed.