This paper draws on data from a larger research project conducted in a European country: a longitudinal study of choices and values in teachers' work trajectories. It is based on unique material, namely interviews on ten occasions via email with 87 graduates from a Teacher Education programme regarding their work as teachers, spanning from their graduation in 1993 up to present day. This paper reports results from one of the studies dealing specifically with teacher commitment, and focuses on the meaning of teacher-student relationships for teacher commitment. Positive teacher-student relationships are vital for student learning (Cornelius-White, 2007). Teachers invest emotionally in their work and engage in their students, and if they are to be effective in helping their students learn they must be able to deal with such challenges in a successful way (Day & Gu, 2007) and committed to student learning (Gu, in press). Even if commitment is linked to the individual, it is mediated by the context (Day, Sammons, Stobart, Kingston, & Gu, 2007; Sammons et al., 2007). This paper explores sources of teacher commitment in challenging conditions. 87 informants answered interview questionnaire on ten occasions, annually for the first four years and then at intervals. The questions related to their lives and work. For an overview of the material see (Lindqvist, Nordänger, & Carlsson, 2014). In this paper, the main focus lies on two questions asked during the third year of data collection: In question 3:3 informants were asked to describe one student that had caused them trouble during their last school year, and in the next, 3:4, to describe one student that have given them much joy during the same period. Surprisingly many described the same student in their answers to both questions. The analysis aims to explore features that elicit commitment in challenging teacher-student relationships. Preliminary results point to three sources of commitment in challenging teacher-student relationships: First, to conceptualize problems as challenges stimulates the informants' intellectual capacity. Second, to help a student in trouble is viewed as central in their professional responsibility, and third, to witness students' progress strengthens their self-confidence. Commitment is important for student success and for teacher retention, and to get a deepened understanding of sources of commitment can help all teachers teach and students learn.