I need to ask a favor of all of you. Please read the following quote from Kenny's blog:
"Yesterday it occurred to me that one of our greatest struggles as we try to relate to other people is our need to objectify ourself. What I mean is that, paradoxically, although we have so much more information about our own experiences than anyone else's for this very reason we often cannot understand ourself. We lack the context to understand ourself as a human being precisely because we have such a skewed perspective on ourself, and we struggle to fit ourself into the role of human as we cannot compare ourself to anyone else since we lack comparable data on any one else's experiences. Thusly we struggle to objectify ourself, or to consider our experiences from an objective, rather than subjective, point of view, because that is the only way that we can relate to other people, whom we must all view, to some extent, from an objective perspective."
Now, in case that was too academic for you...
We try to apply labels and roles to ourselves because that's the only way we can relate ourselves to other people. We're too complex and confusing to do it any other way.
There's some stuff later in the same post that I also want to talk about, but I'm just going to use my own words for it. Go read his post as well if you want, though. I've linked to it at the top of the page.
I have this theory that other people anchor us to ourselves, and to life. When other people are involved, you define yourself by how you relate to and interact with them. When a person leaves, be it leaving your life or leaving the room, you lose some of that stability.
You become less boxed-in, and more of a seething mass of perception, emotion, and thought. This isn't necessarily bad-- just scary, and sometimes hard to deal with depending on the degree. I think that's one of the many reasons other people are important-- figuring out them helps us to figure out ourselves. At the very least they make it easier to live simply by being something on which to hold:
"I am customer. Ze is salesman." "I am Ze's friend." "Ze is my mom." "Ze is a fellow tourist."
Those are gross simplifications, but you see my point-- defining the relationship between oneself and Ze allows you to in turn define yourself in relation to Ze. You can stand up and say "I am this for right now." And that's usually a comforting ability to have.