The stronger the emotion you feel from some event in your life, betrayal, or a trauma or whatever it might be.
The more altered you feel inside of you, the more you pay attention to the cause outside of you. The brain takes a snapshot. It freezes an image and embosses that pattern neurologically in the brain. That's called a memory. We create long term memories from strong emotional events.
Some people have a stronger experience in their life, and it catches all of the brain's attention. So now they think neurologically within the circuits of the past experience, and they feel chemically within the boundaries of those emotions.
How you think and how you feel creates a state of being. The problem is that if you don't know how to mediate or control your emotional reaction to that event, and you keep that refractory period of chemicals going on for standard periods of time that event produces a chemical change, and the body needs to return back to homeostasis or balance. But if it can't then, the elongation of that emotional reaction for days or weeks is called the mood. You keep firing and wiring the same circuits, and you keep conditioning the body into the past.
So then, you wake up in the morning and you look for the emotion. Now, all of a sudden you keep it lingering for weeks or months. That's called the temperament. You keep it going on for years on end. That's called the personality trait.
So then, a person is memorizing themselves by living in the past...
The latest research on memory says that 50% of what we talk about in our past isn't even the truth. So, we make stuff up about the past. People are reliving a life that they didn't even have just to reaffirm that they can change...