He he... ok, then, explain you. Why do you see yourself as just one person? Why do you see yourself as just you? Why do individuals at all exist? This isn't even philosophy, this is science.
I'm not sure whether you're asking what it's like to be me, or how people in general work. (Science by the way, is a 'how' discipline, not a 'why' discipline.) To try and answer the latter first...
How do we each see ourselves as one person? I think that we tell ourselves a fiction in which we put our actions into a strict, logical sequence underpinned by another fiction called motive. If necessary we retrofit motive to 'explain' our actions to make them look reasonable. A famous example of the latter is the hypnotist who got his subject to open an umbrella indoors and then asked why. The subject said 'to see what was inside the umbrella'.
How do we see humanity as divided into individuals? A possible explanation might be the ease of communicating within the brain (and the brain tends to consistently have the same parts), vs the speed and difficulty of communicating between brains (and those parts come and go). Also, in humanity, individuals compete for sex and food, but mostly sex. It's a big thing for us.
What's it like to be me? Imagine a world in which nobody has faces -- just blank, immobile skin with eyes and a nose and a mouth, but individuals are still distinguishable by the way they move and talk. Imagine that one day they all woke up and took pictures of emoticons, and glued them onto their nose and said 'This is my face. This is how you'll know me'. That's something like my world. I see face-pictures as largely superficial and irrelevant, and I often don't bother with them.
One thing human faces do is show emotion. We often say 'betray emotion', but in fact faces are made to
display emotion -- to send constant messages to one another. If we can't see faces, we can guess at emotion through speech and behaviour, but it's indirect and secondary because it takes longer to work. (Human emotion, by the way, transmits faster than human thought -- so perhaps that's why we're so disposed to seeing individuals as
emotional identities.)
Without faces, the narrative of human emotion becomes much less important. We focus instead on a narrative of behaviour. Without a face, our own emotional narrative becomes less important -- in fact, our individual emotional identity becomes largely irrelevant. We're just a point of observation and action with an occasional sense of mood.
But commonality is important... not agreement on what we can see (because different points will see different things), but commonality on what is observed and what its behaviour is.
If we have a face we can talk about 'God' and send complex face-pictures to one another. Even if we can't find a 'God' in our world, it exists for us as a bunch of face-pictures. Others can copy our face-pictures (and copying expressions stimulates emotion) and begin to share our fantasy too. In fact even while people are arguing over what 'God' means, they can be sharing exactly the same emotions, so they may agree that it exists, because their emotions feel the same. Perhaps that's partly why an important part of the God-myth is that God has our own face -- God feels as we feel. But without a face, if we talk about 'God' we actually have to go and find an object and point to it.
That's much what it's like to be me.
Without an object to point to, 'God' for me is nothing more than some fantastical stories and a code for a collection of face-dances. I don't believe the stories, and I'm not terribly interested in the faces.
And our shared world... for me it doesn't have a human face. It doesn't have a face at all. Like me, it is just behaviour.