All of us experience self-change in relationships, but our subjective experiences of change may not always align with external metrics of such change. We hypothesized that people with higher attachment avoidance are more likely to experience self-change as a loss, which in turn predicts lower relationship commitment. We further hypothesized, however, that there would be a disparity in perceptions, such that avoidant people will experience self-loss that external metrics-including their own behaviors and ratings from third-party coders-do not detect. Results from four studies, which employed a variety of cross-sectional (Studies 1 and 4) and longitudinal (Studies 2 and 3) methods, demonstrated that higher attachment avoidance predicted greater experienced loss of self, which in turn predicted lower commitment. Studies 2-4 also revealed evidence for the hypothesized disparity in perceptions: Avoidantly attached individuals' experience of greater self-loss failed to emerge when using a variety of external metrics of self-loss, producing Avoidance × Loss Type (experienced vs. external metric) interaction effects. These studies suggest that avoidantly attached people, who tend to be vigilant to autonomy threats in relationships, experience relationship-linked changes as losses, even though external metrics fail to detect such loss. (PsycInfo Database Record (c) 2024 APA, all rights reserved).