He is engaging in something called "rumination".
Rumination is a sort of fanatical over-thinking in which an individual will rationally replay a past negative occasion over and over however gain no genuine ground toward goals. It is like stress in that an individual will fixate on the potential causes and outcomes of an occasion; be that as it may, stress is identified with future occasions, while rumination is identified with the past.
Rumination can be turned off by two great strategies: 1) escape the negative neural systems and 2) handle one issue at any given moment with arranging.