Although previous research has indicated that forgiveness is an essential part of relationships that thrive, forgiveness tends to become increasingly difficult as the intensity and duration of hostility rises. Understanding conditions that help make forgiveness more possible, as well as those that actually make forgiveness more difficult, then becomes an important asset for clinicians promoting healthier relational dynamics and longevity. Using data from 257 participants across two time points, we measured the association between hostility and forgiveness to test the moderating role of attachment. Greater hostility was linked with less benevolent forgiveness and more resentment. Moreover, anxious attachment moderated the association between hostile interactions and resentment—the inability to forgive. Implications for helping professionals and clinicians are discussed.