The activity of self-tracking is an emerging trend that often involves adopting wearable technology. Vendors promise new personal insights and opportunities to optimize health and lifestyle by adopting such devices. Spurred by these promises, users are also driven by curiosity and exploration to adopt and use the device with the aim of quantifying the self for the purpose of self-knowledge through numbers. We investigate the interplay of technology, data and the experience of self during the adoption and use of wearable technology as a pre-commitment device. The empirical focus lies on two self-tracking devices, which track moving and sleeping activities on a daily basis. 42 interviews were conducted with users of self-tracking devices. The findings suggest that self-tracking activity through wearable technology does not necessarily lead to behavioural change, but predominately works as a re-focusing device. In this light, the user experiences tensions between rational and emotional behaviours when reflecting on personal data. The results contribute to a more nuanced understanding of adoption of the emerging wearable technology in daily life and how users deal with the personal data by developing coping tactics, such as disregard, procrastination, selective attribution and neglect.