Self-tracking technology can help users develop new knowledge about themselves, supporting their health and general wellbeing. Most of these devices inform users about their lives by autonomously generating data about highly constrained topics. Recent research has started to explore more flexible, manual self-tracking systems, which allow users to express themselves through their data and learn by engaging with their experiences in-the-moment. This article describes a field trial using the Chromatize app, designed to explore the value of minimalism and flexibility — including in data histories — in personal tracking systems. Our data indicate that low-burden experience logging systems which focus on the creation of symbolically-rich, self-defined data can support self-awareness, reflection and regulation at opportune moments. The analysis also contributes a formulation of reflection in the context of self-tracking technologies that is more meaningful than the loose use of ‘reflection’ used in much of the literature.