Exposure and response prevention is the most strongly supported treatment we have for OCD, and yet most clinicians can name a patient for whom it seemed to stop working or never worked for. The usual response is to intensify the protocol or try something else and that instinct is often wrong. In our experience, apparent ERP failure is rarely a failure of the treatment itself. It is far more often a diagnostic problem or an application problem. Oftentimes, the presentation is not OCD or not only OCD; the patient is measuring success by whether their anxiety dropped rather than by what they were willing to do; or the exposures are touching triggers while the core feared outcome, and the mental rituals protecting it, remain untouched. What is missing in most settings is not effort or fidelity to a manual, but a structured way to work out which of these is happening before changing the plan.