Lack of sleep hygiene is a widespread problem that drives the demand for sleep-tracking technologies. Prior research discussed the dark side of self-tracking technologies, but research specifically on sleep-tracking technologies is scarce. This study explores what potential stressors users attribute to sleep tracking executed through a smart ring. We conducted 38 semi-structured interviews and used thematic analysis to identify eight potential stressors in the context of sleep tracking. These stressors include complexity, invasion, inaccuracy, unreliability, data-feelings discrepancy, the pursuit of perfect data, vague guidance and interpretations, and overload with multiple self-tracking technologies. We further theorize these potential stressors using the person-technology fit model. The paper contributes to the nascent IS research on technostress in the context of sleep tracking.