How can a person forge a stable ethical identity over time? On one view, ethical constancy means reapplying the same moral rules. On a rival view, it means continually adapting to one's ethical context in a way that allows one to be recognized as the same practical agent. Focusing on his thinking about repetition, I show how Kierkegaard offers a critical perspective on both these views. From this perspective, neither view can do justice to our vulnerability to certain kinds of crisis, in which our ethical selfunderstanding is radically undermined.