A 28-year-old woman is referred for therapy after her mother was diagnosed with terminal cancer. In sessions, she presents with an exaggeratedly cheerful demeanor and insists she is 'totally fine' and 'just so grateful for every moment.' She volunteers excessively at her mother's hospice, brings elaborate gifts to every visit, and becomes angry when family members express sadness, telling them they should 'stay positive.' Her therapist notes that the patient's affect appears rigid and incongruent with the gravity of her situation, and she becomes intensely anxious during brief moments when sadness begins to surface. Which defense mechanism is the patient most prominently utilizing?