Long COVID is a new illness, and we still lack medical knowledge about possible treatments. This has led to the independent adoption of fitness tracking technologies for the management of long COVID. Through semi-structured interviews with 21 people with long COVID who used fitness tracking technologies, we found that fitness tracking devices were used to pace energy through finding correlations between activities and data, provide proof of illness to themselves, healthcare providers and friends and family, and to help gain a sense of agency and control during a new and enigmatic illness. Our findings support and extend design openings for the development of “pacing technologies”. These include the importance of customization and supporting the user in their recovery if appropriate, applying strategies for mitigating anxiety when tracking, facilitating the sharing of pacing data with friends and family and healthcare providers, and supporting users in identifying the optimal components of rest.