I know most will not buy into this line of thinking and reasoning because most of us are too tied into our commonsensical notions about reality. Nevertheless, what I am going to write here has me convinced about its truth, though you may not be in agreement. Here goes.
We are not what we are taking ourselves to be. Take the body. It can be analyzed down into its constituent atoms and subatomic particles, which physicists are quick to tell us that those subatomic particles are not matter in the sense we tend to think of matter as physical lumps of some substance, however infinitesimal, but rather they are mathematical entities exhibiting some mathematical properties and finally best conceived as forms of energy.
Moreover, it is not the body that is giving us the sense of an “I’. It is the mind that is constantly manufacturing thoughts of an “I” (you could call it the “I-thought”) centered around identification with body as being oneself and thinking that all those thoughts and feelings also being thought and felt by that “I”. The mind is basically a self-referential system validating itself by itself.
But, a closer examination will reveal that there is also some other entity that is aware or conscious of all these things about the body and mind. You could try to claim that that awareness or consciousness is nothing but the mind itself being aware or conscious of its own functioning. But, to the extent that a mind is something that thinks, and since awareness or consciousness is distinct from mere thoughts, we will be hard put to justify the claim that even that non-thinking substance is also mind.
Hence, we can see that there are seemingly three entities that present themselves to one’s enquiry – a body, a mind, and consciousness or awareness. Now, we cannot be an agglomeration or combination of all these three because it does not make sense to conceive of an “I” as being in turn composed of three other distinct entities. Thus, if we have to choose between those three entities as one’s true identity, one realizes that whatever one is one has to be that constantly and enduring through time and not subject to change because one cannot claim a changing entity as being oneself since then we will be applying the term or word “I” to very different entities. And, since body and mind in the form of thoughts are subject to change, they cannot be the true “I” – so, the “I-thought” being manufactured by the mind which is associating itself with different entities across time as being itself, like the changing body, thoughts and feelings, as in “I am lean”, “I am intelligent”, “I am sad” cannot be the true “I”. So we are left with only Consciousness or Awareness as the only possible candidate for being the “I”.
But, note that Consciousness or Awareness being an attributeless and indivisible entity it cannot be two. Not being two, it cannot even begin to say “I” meaningfully because the personal pronoun of “I” makes sense only when there is a “not-I” or “another”. But, there is no “not-I” since both the body and mind can be shown to be nothing but names-and-forms of Consciousness or Awareness, and thus mere appearances which do not really exist but only seem to (see https://self-realization.blog/2018/09/18/everything-is-consciousness/). Only Consciousness is. Naught else is.
I will leave it to you to work out the radical implications of this on how to live your life.