I am my right arm, although I have a left arm. A sense of ownership versus a sense of being one with. I enact the most complex movements I want to execute with my right arm. It seems to execute my movements immediately and fluently. This sense of uncomplicated immediacy, the fact that the route from my conscious thought to my movement is so rapid, is probably what grants me the feeling of being one with, or inhabiting my right arm.
My left arm is a completely different story. It feels like a tool for me most of the time. It feels clumsy and a bit stiff when I try to execute complex movements with it. I can hold the tomato in place with my left arm, while chopping it with my right arm, but not the other way around. I am usually more aware of the existence of my left arm then I am of my right. The former is a small fleshy presence next to my torso. The latter is transparent to me. It was simultaneously surprising and not surprising to me to discover that my right hand is slightly more developed and large than my left.
Injury disconnects my feeling of being one with my right arm. The strange sensation, pain, damage to my normal range of motion, causes alienation. I now have a right arm. I need to stabilize it a bit in space next to my torso. When my left arm is injured it is made even more alien to me than it already is.
Perhaps it is the immediacy with which my right arm corresponds to my conscious thought that makes me feel I am it. I have a somewhat similar relation to other humans that are very close to me. If someone is close to me to the degree that he or she can instantaneously grasp what I am feeling (and I was blessed with the ability and opportunity to forge such connections), I have a feeling that we are no longer completely separated from each other.
Does this stream of thoughts bring me closer to the question of why most of the time I have a feeling of objectification/alienation regarding my body, while feeling unity with my mind? Immediacy seems to be the answer. My conscious thought immediately reflects my conscious thought. But this is a tautology. And I am no less my flesh than I am my conscious thought.