A series of obstacles (status precariousness, high turnover, employer repression, negative work conditions, union weakness and lack of a tradition of struggle and so on) explain why the mobilization and the unionization of workers are unlikely in precarious and flexible sectors. By studying strikes that happened in a bookshop specialized in art books and in a cultural supermarket, the authors show in what conditions these obstacles can be overcome. If the workers’ motives of discontent are to be found in their trajectories and in the disappointment of their hopes of self-realization in work, their commitment in the strikes is related to dynamics and solidarities internal to their work group. Even when painful, the experience of the strike opens up a practical initiation into collective action, which can initiate trade union careers.