When teachers participate in training to nurture their own and/or their students’ social and emotional (SEL) skills, it is likely that change occurs both in their teaching, their relations with students, their own levels of stress, and their broader reflections on classroom processes. However, little research has explored these changes in teachers. This paper presents the results from a thematic analysis of the process diaries of teachers involved in teacher training in social and emotional learning (SEL) in Sweden. Twenty-nine out of the 122 diaries available were analysed until saturation was reached. The following themes and sub-themes were extracted: development (professional and personal, and classroom climate), and concomitants of development (need for collaboration and unease). The themes and sub-themes are related to theoretical aspects of specialised teacher education and to the debate in Sweden on how to proceed with SEL programs, and more generally with life skills programs. Results suggest that training generates both general teacher improvement and better implementation of SEL programs.