Running the changes on pronomial constructions produces a kind of triangulation of subjects, including but not limited to the subject that is you, but this only fascinates without yielding any structural flaw since it is an effect in language. Whether it is cause or effect or neither remains unresolved. Simpler and more naive is to note that while all things flow, solidity having the nature of a standing wave,  some things flow more slowly than others. The self is actually an illusion of stationarity and even the web of subtle feelings that seem to cluster around its absence have a peculiar persistence. This is enough the case that you can focus, at least in the form of an open intention, on what doesn't change at all and take this as a ray leading straight inwards. This has nothing to do with the argument that to perceive change the perceiver must be unchanging. The argument is doubtful and at best might lead to another version of the maze of perspectives. No, it a matter of direct inquiry, again as naively as you are capable of.