Our souls as well as our bodies are composed of individual elements which were all already present in the ranks of our ancestors. The "newness" in the individual psyche is an endlessly varied recombination of age-old components.
We cannot, even given our most imaginative efforts, construct a concept of Self that does not impute some causal influence of prior mental states on later ones.
Or is anyone's identity a matter of fragments held together by convenient or useful narrative, that in ordinary circumstances never reveals itself as a fiction? Or is it really a fiction?
It is with our entire past ... that we desire, will and act ... from this survival of the past it follows that consciousness cannot go through the same state twice. The circumstances may still be the same, but they will act no longer on the same person ... that is why our duration is irreversible.
To be a healthy person, you have to be sympathetic to the child you once were and maintain the continuity between you as a child and you as an adult.
We are the same people as we were at three, six, ten or twenty years old. More noticeably so, perhaps, at six or seven, because we were not pretending so much then.
Identity in the form of continuity of personality is an extremely important characteristic of the individual.
I am still every age that I have been. Because I was once a child, I am always a child. Because I was once a searching adolescent, given to moods and ecstasies, these are still part of me, and always will be.
I think if characters change too much, it's unrealistic; their whole fabric of who they are as a person doesn't just disappear.
As we have seen there is some kind of continuity in any case since every experience affects for better or worse the attitudes which help decide the quality of further experiences, by setting up certain preference and aversion, and making it easier or harder to act for this or that end.