If at this moment, you're worried that I plan to present myself here as the wise old fish explaining what water is to you younger fish, please don't be. I am not the wise old fish. The immediate point of the fish story is that the most obvious, ubiquitous, important realities are often the ones that are the hardest to see and talk about. Stated as an English sentence, of course, this is just a banal platitude -- but the fact is that, in the day-to-day trenches of adult existence, banal platitudes can have life-or-death importance. That may sound like hyperbole, or abstract nonsense.
A huge percentage of the stuff that I tend to be automatically certain of is, it turns out, totally wrong and deluded. Here's one example of the utter wrongness of something I tend to be automatically sure of: Everything in my own immediate experience supports my deep belief that I am the absolute center of the universe, the realest, most vivid and important person in existence. We rarely talk about this sort of natural, basic self-centeredness, because it's so socially repulsive, but it's pretty much the same for all of us, deep down. It is our default-setting, hard-wired into our boards at birth. Think about it: There is no experience you've had that you were not at the absolute center of. The world as you experience it is right there in front of you, or behind you, to the left or right of you, on your TV, or your monitor, or whatever. Other people's thoughts and feelings have to be communicated to you somehow, but your own are so immediate, urgent, real -- you get the idea. But please don't worry that I'm getting ready to preach to you about compassion or other-directedness or the so-called "virtues." This is not a matter of virtue -- it's a matter of my choosing to do the work of somehow altering or getting free of my natural, hard-wired default-setting, which is to be deeply and literally self-centered, and to see and interpret everything through this lens of self.
People who can adjust their natural default-setting this way are often described as being "well adjusted," which I suggest to you is not an accidental term.