The aim of this qualitative study is to explore adults' motivation to learn mathematics in the workplace and the role that the trade union education approach promoted in the United Kingdom plays in that motivation. The findings draw on data from 20 semi-structured in-depth interviews with adults learning mathematics, organised through their trade union representatives. Trade unions promote education which uses teaching and learning approaches based on collectivist and activist principles, which is different from mainstream education, so the research explores what might be learnt from this approach. The findings show that the trade union-led approach enables even long-held negative feelings towards mathematics to become positive. The research finds a strong link between supportive social networks, including Union Learning Representative, as well as positive social and emotional encounters in the classroom that develop adult learners' confidence, increasing their motivation to both learn and use mathematics in their everyday lives. This change in feelings and motivation is termed an "Affective Mathematical Journey." These findings, while taking place in a non-traditional context, nevertheless are relevant to practitioners working with adults in both traditional (school and college) and non-traditional (workplace and community) settings. There are also indications of the positive influence this learning has on the relationship between individual members and their trade union organisations.