Some believe the self is some intrinsic core with immutable fundamentals. Some believe the self is a Ship of Theseus. Some believe the self exists only in the present instant, and all past and future moments are inhabited by some Other. I believe each of these has some truth to it, and are largely dependent on exactly what one means by "the self".
I think the view of the self as only existing in the instantaneous present is a good place to start. Essentially, in Quantum Theory there is a concept of the Planck Time, which, without getting into technical detail, is the smallest unit of time that makes sense in the mathematics of Quantum Theory. One can look at the time stream as a series of "frames" that last one Plank Time each. After all, if the universe was not static between those frames, then that would mean something happened between those frames, or, in other words, some even took less time to happen than the shortest possible time, which Quantum Theory says is impossible. Whether that's ultimately the absolute truth of how the universe works, that's unknowable. But this way of looking at time implies that one might only be said to exist as the "current self" one fame at a time. If so, then the past self is a completely distinct entity, and the connection to the current self is only in terms of inherited qualities. One might look at even their past self from one frame ago, and consider that entity to not be included in their "self" and instead be no more connected to them than their parents or grandparents are - simply an ancestor from the previous instant, from which the current self inherits nearly everything.
This view of the self isn't popular, since we perceive continuity. We might not truly exist in continuity (again, we don't know for absolute sure how the universe truly works), but generally, continuity of the past into the present is included in the concept of the self. The Ship of Theseus is perhaps a less absolutist way to view the separation of current and past selves, maybe as a way to accept that the self has no constant qualities. If our selves, like the metaphorical ship, are simply having "parts" replaced with different ones as we learn and change our behavior and traits, then our continuity exists from instant to instant, but does not imply some fundamental constancy. From this perspective, the only truly continuous concept of the self would be to include the entire history of the person, changes and all, as the "full self". Trying to define a break in continuity in this framework runs into the same problem as the Ship of Theseus does in trying to define a distinction between the "old ship" and the "new ship".
This is all assuming that the self can change completely in the first place. Maybe there are some fundamental qualities we cannot change, and that intrinsically define us no matter how much we change and grow. This rapidly becomes more a spiritual question than a philosophical one, because it essentially requires a concept of a "soul" or "intrinsic nature" which, in the physical world, is not something that applies to anything except the quantum fields themselves, the most foundational elements of the universe. But still, perhaps there is some unknowable, yet immutable, element of one's nature that is tied to the spiritual realm, whatever form that takes.
Alternatively, one might simply consider the immutable past to be the part of the self that cannot change, since no matter how we change with time, we can only move forward from an unchanging life history. Maybe the elements of the self we picked up along the way, the connections and understandings from our life experiences, are the only things about ourselves we cannot change.
These days, I tend to lean more toward the final explanation, since it seems to be the most useful for self-improvement and mental health.
The instantaneous-present-only self might be technically correct (insert The Princess Bride reference here), but it isn't really a useful framework for developing emotional intelligence, since it allows one to pass responsibility for past choices onto the "past self" far too easily, and unless one is careful, it allows one to ignore the impact the past has on the current self.
The "Self of Theseus" is true in some sense, and is not necessarily mutually exclusive with the idea of a self with some constants, since as mentioned in the final interpretation, the whole past can be included in the self, which both allows the current self to be wholly different from the past self, while still including the past self in the wholistic "self" concept. Still, there is a tendency to imagine that one has morphed into a completely different person than the past self, which I would argue still rejects the reality of how the past self shapes the current self.
Simply put, one thing I have found over the recent few years is that the past still lingers in myself, in one form or another. I have been rediscovering past memories as my mental health is improving (2021-2022 was a rough time for various reasons, most of them my fault), and with those memories have come answers to questions I hadn't asked. Those answers have been useful for me to fill in more of my own self-concept, finding places to put pieces I left behind a while ago. I don't necessarily think I was "broken" before or anything so dramatic, but I think I was messy, and missing some pieces I used to have.
Slotting those pieces into the current self has made a lot of things make sense that did not before. Notably, one major effect of this is that I now have explanations for elements of myself that I previously had to explain with intrinsic qualities. Without the foundations they came from, these elements seemed mystical and nebulous, but now they make sense. It feels good! It's not just curiosity being satisfied, but it's a greater confidence in my own mindset, or, a greater understanding of how I need to change it.
These pieces are still parts of me. They are my foundation, even if they were lost in cobwebs somewhere in my pre-university brain. Sometimes I love what I see, sometimes it's just a simple "oh, okay, makes sense" moment, and other times, I hate what I find. But the most important thing I keep in mind regardless - theses are all part of me, for better or worse.
I know it's technically possible to reject this notion, as explained earlier. Many people seem to do just that, preferring to leave their past self alone, and act as if they can live like that was never their current self. And maybe for some, for the mental state they find themselves in, that's easier than the alternative of coping with what they find in their own cobwebbed mind-basement. As much as that sounds like an Evanescence song with how edgy and gloomy it is, that is a belief many have about themselves. I remain skeptical about that in their case, but I can't honestly claim to know they're wrong. However, in my case, I don't see any other way forward. I must accept my foundation because it is reality. It objectively, provably, happened in my past, and how could my present NOT be affected by the past, the former present? If I was me in the past, then I came from past-me. I would disservice myself to ignore that fact.
The past is a learning opportunity about the self, as I have discovered, and with what I learn of my own past, I better prepare myself for my own future. I have more tools, more weapons, to face the future and its challenges, by taking advantage of every part of my past. In Kung Fu Panda, Master Oogway may have only referred to the present as a gift, but the past is a gift too! It's a chance to give myself constructive feedback - that's what the feeling of embarrassment is really for. Shame is instructive. Cringe is empowering.
Do I consider my past self to be a separate being? In some ways, yes, but in other ways, no. We have different motivations, but we share much of our foundation. I simply have more foundation laid than past-me does. On one side, it's easy to look at past-me and see someone blinded by ignorance, making choices they didn't have the tools to understand. But on the other side, sometimes past-me had the tools to make a better choice, and didn't bother to check. As someone who has had to teach themselves social interaction by learning rules explicitly rather than by feeling out intuitively, I'm not sure how to feel about my past ignorance - maybe there was some clue I missed in the moment, maybe I would never have noticed without the benefit of hindsight. It's not like failure isn't part of the learning experience, after all.
Whatever guilt I feel at my past, it's worthless if I don't do something about it. That's something I've been teaching myself lately. And now that guilt is useful, now that failure has a potential upside in the meta-context, I don't fear them as much as I used to. As that fear lapses, so does the motivation to distance myself from my past self. No need to avoid the facts. No need to absolve myself. It's not about avoidance or absolution; it's about learning and progress. Without my past as source material, those are impossible.
Thanks for reading, and I hope you too make peace with the cringe in your own past.
Have a great whatever!
~ Bonkie