Destructive nostalgia

Excessive amount of nostalgia and grieving for the past to the point where present and the future becomes irrelevant for the person. This can be mostly caused by lack of happiness in the present and depression. The name destructive comes from the fact it causes destruction of the future due to being demotivated to do anything for it.

Patient: "The present and future has nothing for me, the brightness of my lost past is corroding my mind."
Therapist: "That sounds like destructive nostalgia."