I have had this all my life I think, and I really struggle with my identity because of it. I feel like each time my life falls apart I lose myself. I never become the same me as before "things went wrong". And I feel I am just so many broken parts of me, so many parts of me too painful to connect to or return to, because of memories of that specific period and the losses involved. I'm not sure why it all falls apart each time, it feels like some kind of disappointment each time which triggers it, but when it starts I cannot stop it and I feel really powerless and fragmented because of it

Researchers Have Investigated “Derailment” (Feeling Disconnected From Your Past Self) As A Cause And Consequence Of Depression
We move house, change jobs, begin new relationships, yet most of the time, most of us still experience a thread of inner continuity – a constant feeling of me-ness that transcends the various chapters of our lives. Indeed, there’s evidence that having a stable, constant sense of self and identity is important for psychological wellbeing. However, this thread can rupture, leading to an uncomfortable disconnect between who we feel we are today, and the person that we believe we used to be – a state that psychologists recently labelled “derailment”.
Article:
https://digest.bps.org.uk/2019/06/03/researchers-have-investigated-derailment-feeling-disconnected-from-your-past-self-as-a-cause-and-consequence-of-depression/