This may actually come as surprise to those who've heard me talk about particle physics before. Not that I'm anything more than a semi-educated layman in these matters, but I do try to explore the more scientific side of some New Age ideas. (Fun website: phdcomics.com)
In essence the particle theory is that ALL known matter (skip dark matter for now)- are comprised of the same sub-atomic particles. So that means everything from you to the sun to your computer and everything is, at its smallest known level, exactly the same. So seems kinda easy to make the jump that we're all the same at a macro cosmic level too, right? What about holographic universe, that the entirety is contained in the piece? Well, there is a reason these calculations are still called theories. All my examples can be extrapolated to reflect other possibilities and interactions.
Back to the point (I swear I have one) is that while the particles seem to be limited (previously unknown interactions are being discovered at a phenomenal rate), but combinations built on combinations are not. You are not a star at the moment. You are presenting as human (or at least mostly so). Your computer is not a coffee mug and so forth. I am not you, nor am I even a reflection of you, or you of me. My combination is not yours.
The concepts of "we are all one" and "everything in the universe is a reflection of you" are ripples of monotheism. (An interesting blog article that gave me the idea for that phrase can be found here: Confronting the Black Hole) When we realize that we are indeed our own sovereign entity, when we recognize our interactions are with other entities in their own combinations-of-existence, we can recognize diversity as positive. The "we are all one" narrative is downright harmful when someone uses the concept to perpetuate their own idea as "the way it should be for everyone." E.g. theology in politics. Or assuming that privilege doesn't exist, we're all African, etc. (Those are some very weighty topics on their own, but the underlying theme of we're-all-the-same is pervasive.)
A gift of recognizing we're not all one is to stop comparing ourselves to others and allow us to be in the moment with who we are. My partner and I are not "one", we are two individuals who choose to walk our paths together. We do not assume each other to to feel, think, or see the same way. To recognize that we have the ability and right to own our individuality and to change by informed choice is incredibly empowering. Here's where it really gets hard: figuring out who you are! That can be frightening as well as freeing. Fortunately, this is a process not a result. Have things in common. Share likes and dislikes with others, but let go of the assumption that everyone is you. They're not, and when you acknowledge that you can actually see them for who THEY are, not as you want them to be. The implications are enormous, but just for today, really LOOK at someone consciously and without expectation or judgement. Who is there?