Despite decades of policies to widen participation in medical degrees, students selected for Medicine continue to reflect a socially elite group, rather than the diversity of the communities that graduates will serve. While research has documented experiences of students from disadvantaged backgrounds, this paper examines the "cultures of success" that enable advantaged students to gain entry to medical school. It documents how these students' school and home environments enable the development and realisation of "aspirational capacity". Aspirational capacity is not just about having a dream, but also the resources and knowledge to realise one's dream. The paper also examines a negative side of a narrow aspirational focus. "Aspirational constriction" describes the premature foreclosure of career ambitions, which can have negative implications for both the students and for society, and for less advantaged students, who are effectively excluded from degrees such as Medicine.