The mental diseases affect the entire personality, while the most current physical injuries damage only some parts of the personality, though they change entire states of mind.
The failures which happen in our social and emotional life are received as if they would be in the category of physical diseases. We accept that they alter our states of mind and moods, but it is more difficult to view them as altering our entire personality.
Only when the failures follow one after another very fast, we start to perceive ourselves as wholly modified by what happens to us.
In the case of life events, the rhythm of their succession is subjectively measured. An external observer may see someone as being overcome by the rhythm of the bad happenings, though that person has not the same perception.
Therefore, perhaps we become unconsciously different from us because of the failures like any person affected by a mental disease. And from lunatics we should learn that the past healthy state is not a matter of regrets.