There can be confusion over what is meant by no-self in various meditative traditions. It’s not the claim that people are illusions, or that you can’t say anything about the psychological or biological continuity of a person. It’s not mysterious that we wake up today as ourselves and not someone else. These are not the puzzles being addressed.
The core insight, the illusion that is cut through, conceptually and experientially, is our apparent normal default condition of feeling like there is a subject in the center of experience. Most people don’t merely feel identical to experience, they feel like they are having an experience, they feel like they are appropriating their experience from some point - very likely in their heads - the witness, the thinker of thoughts, the willer of will, the guy in the boat who has free will, who can decide what to think and do next. That’s the default state for almost everybody, and commonplace as it is, it is a peculiar point of view. It doesn’t make a lot of sense, particularly biological sense. It’s not the same thing as feeling identical to our bodies, because we usually don’t feel identical to our bodies, we feel like we are subjects who have bodies, there is a kind of Cartesian dualism that is intuitive. People are ‘common sense dualists.’ As a matter of experience there is this feeling that “I am a subject behind my face.” “I” have a body, am a subject who is thinking, internal to the body, has a body. It is the final representation of the subject that is the illusion.
To put this in neurological terms, let’s just say for the sake of argument at all of this is just neurophysiological events in the brain delivering these representations. It is plausible that any one of these processes can be interrupted, so that you can cease to faithfully or coherently represent a world. You can suddenly go blind, may not be able to name living things but still be able to name tools, suddenly not be able to perceive motion or location, those things can break apart. All kinds of things can be disrupted for the worse certainly. But what these contemplative traditions have recognized is that certain things can be disrupted or brought to a halt for the better. The thing that can interrupt the usual cascade of mediocrity and suffering psychologically speaking is this representation of self as subject in the middle of experience.
You can cease to construct a subject that is internal to the body. What remains in that case is a sense that mind is much vaster than it was a moment ago, because it is no longer confined to the sense that there is this central thinker of thoughts. There is a recognition that thoughts arise all by themselves, just as sounds do, no one is authoring your thoughts - you certainly aren’t. The sense that you are is what it feels like to be identified with this next spontaneously arising thought.
So, you loose sense that you are on the edge of your life, looking over your own shoulder, appropriating experience and what you can feel very vividly here is a real unity. emptyness, non-duality of subjects and objects, such that there is really just experience. This is not a new way of thinking about yourself in the world, this is a ceasing to identify with thought. This is making no metaphysical claims about how this relates to matter or the universe.
As as matter of experience you can feel identical to experience itself. You are not standing on the river bank watching things go by, you are the river, and that solves a very wide class of problems, psychologically speaking, with respect to suffering. And, it does land one in a surprising kind of equanimity and even eudemonia (well being) that may seem counter intuitive in the midst of the cacophony of daily life. But again, it’s not about the negation of personhood, it is just a recognition that as a matter of experience there is just experience, and the feeling that there is an experiencer is yet more experience, so that if you just drop back… there is just everything in its own place.