Such words perfectly encapsulate the sense of deficiency that a person might experience when ostracised, when unable to fit in.
There is nothing egotistical in the last stanza. He was there one minute, but the next gone, and replaced by mere air - intangible, insubstantial, invisible.
He becomes careful not to disturb the wholeness of things in the environment.
It should be taken as a whole. Until he moves. He is describing himself - his person - as a void.
He feels that he is fragmenting, disturbing and damaging the natural wholeness that is why air moves to fill the spaces occupied by his body while he walks. The poet indirectly pleads human beings to fill the gaps in the nature if they separate the parts of nature.
The poet moves forward and he parts the air but it becomes whole again. The last stanza suggests that we all move to make a whole, not part. This negativity towards himself is what the entire poem is focused on.