The structure of an individual remains largely set before birth and continues through unto death. Human structures are made to change through growth and life unto death, and change is part of the structure. Yet entangled particles make up material forms, and though the individual particles may change the energy that makes the particles and the form of a structure remain the same.
There is water behind a dam. One may jog past a dam every day and admire the wonderful reservoir and sparkling blue lake water, and know that the water is different each day, yet the same form for the lake itself remains. Platonic forms have relevance in the actual quantum structures of things in a way with entangled particles existing in forms. Actualized forms remain until their time is passed.
Individuals can remember their earliest years- memories persist of being age 3 or 4, and one knows oneself that one’s self is the same knower of self that always was (in most people); one is just at a different space-time place on one’s wordline of experience and existence. If brainwashed sufficiently one can have false ideas of self I suppose, and if weak willed enough can believe they change who they are as quickly as the weather. with no continuity in who they were before. In the math question of how long did it take for the car-self to travel from point A to point Z at the speed of life they answer; ‘the car self was never itself having changed at every point on the way and is not-self at point Z and all other points where it never was.
Maybe it would be reasonable to compare the process of being oneself and aging to the experience of making a journey with one’s own legs or oars and arms a certain distance, where one can recall the past few miles and reflects that it is easier going now, with fewer waves or clouds of insects hovering about, than it was then an hour or two ago. Then when a year passes one can remember that journey and how tough though enjoyable it was, and wish perhaps that once again they were on that journey, or a similar one ahead. One tends not to think- “I am not now who I was then”. One knows that one accumulates experience and goes through new situations. One is the same self yet changed with additional knowledge, living in the present instead of the past.