Is living a specifically and ultimately personal enterprise?

Here are some similar ideas:

• Metaphysical Solipsism: Other persons don't exist.
• Evaluative Solipsism: Other persons exist, but their only value is their value to me.
• Narrative Solipsism: Other persons exist, but their narrative identity is defined entirely/ultimately in terms of my life.
• Total Epistemic Solipsism: Other persons exist, but I can't at all know what it's (qualitatively) like for them to live.
• Partial Epistemic Solipsism: Other persons exist, and I can know some of what it's (qualitatively) like for them to live, but not all of it.

These ideas were the only ones I could come up with right now. Do any match what you're getting at? Perhaps a combination of these ideas?

(Though you do reject the first item on the list, I included it for comparison's sake.)

Epistemological solipsism maps to an I-statement: I only know my own experience. The personal experience of intersubjectivity does not invalidate or violate the fact that I only know my own experience. If others contradict my experience on the meaning of epistemological solipsism then I recognize a semantic disagreement or possible cognitive dissonance arising within my own experience.

In the context of biology there are only chemical reactions, living cells, and nervous system activity in the human body that have no inherent social meaning. Intersubjectivity is the experience of social meaning which arises alongside the experience of non-social causes. In the domain of personal experience the social causes seem to arise as the product of an unconscious cognitive process similar to the processes that Hermann von Helmholtz calls an unconscious inference. The experience that others exist with an independent body and mind occurs only in the context of personal experience and we can explain it using cognitive science as well as we explain perceptions of size, distance, and speed of objects in the 2D field of vision. None of these explainations invalidate or violate the fact that I only know my own experience.

If you are after an understanding of the logic and forces influencing your "personal enterprise". If you are looking into purpose, reason and the path of your existence. Then, I would advise you to get outside the box. Try to see your personal enterprise as part of a bigger structure that has a purpose and reasons on its own. Then you might notice some reoccurring patterns that line up into logic and rules that affect your personal enterprise. It is hard to make sense of the shadows in the cave, without walking out of the cave.

I'd say this is just recognising and accepting demonstrable reality, and it's part of the foundation of truly empathising with others (some might unfortunately also use this as a bad excuse to dehumanise others).

The clearest example of where personal experiences fundamentally differ would be neurodivergence, e.g. autism, ADHD, dyslexia, intellectual disabilities, bipolar disorder or OCD. These conditions have diagnostic criteria and associated behaviours because there are consistent differences in how people experience the world and how they think.

There are also other (direct and indirect) neurological differences not tied to mental conditions, such as other natural neurological variation, differences between genders, and differences in how we experience different tastes and smells and sounds and touch (in terms of whether we like or dislike those, whether they cause side effects like headaches, and how intensely we experience them - there are conditions such as hyperosmia and hyperacusis characterised by a hypersensitivity of certain senses).

Beyond this, one's perspective of the world is heavily influenced by the experiences one has had throughout one's life. There are of course differences in experiences on an individual level, from one person to the next. There are also differences tied to one's race, gender, socioeconomic class, etc. - people in any particular group may commonly share certain experiences with those inside the group, which is less commonly, rarely or not at all experienced by those outside the group.

On a more metaphysical level, one can recognise that you're you, and you only experience what you experience, and not what anyone else experiences. And they only experience what they experience, and not what you experience.

You can, of course, get some insight into what others experience by communicating with and observing them, and trying to imagine things from their perspective (informed by said communication and observation). But that's still not directly experiencing what they experience.

Completely personal, even in the sense that my own family members are so to speak posited as entities for my own enterprise, my own friends placed there such as to grace my own existence with a sense of companionship, or for some other reason.

If you posit this, you can just as well posit

Completely personal, even in the sense that I am so to speak posited as entity for my own family members enterprise, I am placed there such as to grace my own friends existence with a sense of companionship, or for some other reason.

And combined, they show you that in fact, we are all in this together. The grand stage play of life has no singular main character, it has many. Sometimes you are the MC, and sometimes you are in the role of the supporting cast.

It's somewhat difficult to explain this particular perspective,

I do not find this difficult at all. You're in good company as far as I can tell, with a great many philosophers in the past having thought along those lines, and many laymen today as well.

certain experiences the complexity and depth of which I fear I could not live without,

I believe this feeling stems from ignorance about how deep your circumstances can fall until you cannot "live with them" any longer. In other words, if someone says something like this, I assume they mean they value those hard experiences they made in their life, or that those tough phases shaped them in a way they appreciate now.

For example, those others who can wake up every morning at five am so that they can go to construction site and dig holes for eight or nine hours a day - what is their life like?

Just as you say it is. They wake up at 5am and are either happy about that if that timing coincides with their natural rhythm or they managed to consciously adapt to the time; or they are grumpy and eternally unhappy every morning. If they are disposed to working on their own brain, it is possible to make this kind of thing normal and unproblematic (source: am a night owl; am getting up at 5-6am most mornings out of my free decision for reasons not imposed from outside, and am very happy each time. So a sample size of "1" but it is possible). Then they do their physical labour and are either happy or unhappy, but they just do it.

A lot of people are not particularly happy, but still manage to do what needs to be done. Check out stories about big wars (WW1, WW2, ...). People were, in fact, exceedingly unhappy for large bouts in those times, and endured horrible things far outstripping anything any normal person could even fathom without having read or heard about it after the fact. The human (and animal) brain is extremely good at surviving even the worst of the worst conditions.

How can they come back home each night just to have a meal and watch a movie?

They just do. Note that this is not only relevant for physical labourers. Brain workers (e.g. IT, etc.) have exactly the same issue. Even if they just hit keyboards the whole day, their work can be exceedingly horrible if their surroundings are bad enough. They still just do it (until they break, same as the construction workers).

How can these people really exist? And what is their existence like?

Happy or unhappy, but they simply exist. The one is not related to the other. This is not a question of philosophy but of biology. If you assume the general tenets of evolution are true, then it is clear that not dieing is the by far most evolutionary beneficial feature of an organism at all. All the higher level brain functions (emotions, pain reception etc.) are subordinated to surviving (of course, targeted towards it). As far as I know, animals are generally assumed to be incapable of conscious suicide. Even in humans, suicide is the exception, not the rule, albeit it would be very easy for us to do (ignoring our own resistance to it). Everybody is surrounded by plenty of ways to end it all, every day, every second, and still only very few chose this.

I am trying to avoid sounding arrogant or privileged, although in the sense of the latter, I have certainly had my fair share of trouble, it is true.

No worries. Since you are able to communicate via the internet, you and me are for sure part of a small minority of extremely privileged people, when compared to the majority of humanity.

life is a completely and fundamentally personal experience

Yes, you are absolutely right. There is no way to truly experience someone else's life. We can't even solve the problem of "qualia" (i.e., does the red apple look as red to you as it does to me).

my own family members are so to speak posited as entities for my own enterprise, my own friends placed there such as to grace my own existence with a sense of companionship, or for some other reason.

Now you're straying into the world where there is some universal "intent", be it God or Karma or whatever it may be. You are free to think that, there is nothing inherently bad about it (unless it leads you to bad actions like killing your family members because you believe they're just bots placed around you for your entertainment - even if they really were; the other bots (policemen, judges) would afterwards make your life miserable).

I do believe in others' existence. [...] you yourself also possess a specifically and ultimately personal experience

Sure, that's the idea. As valid as the other idea. It does not matter. It would, today, be trivial to replace the whole of Philosophy.SE with a bunch of GPT-5 bots and if you squeeze your eyes and don't look too closely you maybe wouldn't even notice. The ultimate version of "Plato's Cave" analogy.

In short, is living a specifically and ultimately personal enterprise?

In short: yes.

Absol-fucking-utely.

There's nothing more vile than finding out that your hands are tied.

Living can be understood as a fundamentally personal endeavor; however, it is not exclusively so. While our way of life is indeed shaped by our individual worldview, this worldview itself emerges from a dynamic feedback loop. This loop encompasses not only our personal experiences and interpretations but also the sensory inputs derived from our interaction with the external environment. Through continuous observation and engagement with the world around us, we refine our behaviors and perspectives. Consequently, the resulting worldview—and thus the manner in which we live—constitutes a semi-personal enterprise, influenced by both subjective and external factors. This perspective reflects my considered view.