Dealing with emotions is a critical feature of professional behaviour. There are no comprehensive theoretical models, however, explaining how medical students learn about emotions. We aimed to explore factors affecting their emotions and how they learn to deal with emotions in themselves and others. During a first-year nursing attachment in hospitals and nursing homes, students wrote daily about their most impressive experiences, explicitly reporting what they felt, thought, and did. In a subsequent interview, they discussed those experiences in greater detail. Following a grounded theory approach, we conducted a constant comparative analysis, collecting and then interpreting data, and allowing the interpretation to inform subsequent data collection. Impressive experiences set up tensions, which gave rise to strong emotions. We identified four "axes" along which tensions were experienced: "idealism versus reality", "critical distance versus adaptation", "involvement versus detachment" and "feeling versus displaying". We found many factors, which influenced how respondents relieved those tensions. Their personal attributes and social relationships both inside and outside the medical community were important ones. Respondents' positions along the different dimensions, as determined by the balance between attributes and tensions, shaped their learning outcomes. Medical students' emotional development occurs through active participation in medical practice and having impressive experiences within relationships with patients and others on wards. Tensions along four dimensions give rise to strong emotions. Gaining insight into the many conditions that influence students' learning about emotions might support educators and supervisors in fostering medical students' emotional and professional development.