Ask most people to describe themselves and they'll start with a job title, a personality trait, maybe a hobby. Rarely does anyone open with their relationships, or their dependence on the natural world, or their place inside existence as a whole. And yet none of these can actually be separated from any of the others, no matter how neatly they get filed into different conversations.
Four realities emerge once the question of how to live gets asked seriously, and none of them can be dropped without the picture falling apart. There is the self, the human being doing the living. There are relationships with other humans, in family and in society. There is the relationship with nature, since every material need traces back to it. And there is existence itself, all that exists, the widest frame of all.
Notice how tightly these interlock the moment any one of them gets examined closely. A person cannot be separated from their family. A family cannot be separated from the wider society it sits inside. Society cannot be separated from the natural world it depends on for every material thing it uses. And none of it can be separated from existence as a whole, since everything, without exception, exists somewhere inside it.
This interweaving is what gets called coexistence, and it changes the shape of the second big question, how to live. The answer isn't a technique or a productivity system. It's closer to this: study, understand, and live inside coexistence, rather than trying to manage one slice of it while ignoring the rest.
Most modern advice treats these four as separate projects, work on the self here, fix relationships there, worry about the environment separately, on a different day entirely. The order that actually holds them together doesn't respect those divisions, and pretending otherwise is a large part of why progress in one area so often quietly undoes progress in another.