Loner

I think the true definition of a loner is a person who has no real connections with anyone. That could be literal, or simply a feeling of being unlike, or really unattached to anyone else at a deep level.

It is possible to go through life walking next to people, learning to express the correct emotions, even interacting with others without fully understanding what those things mean.

Living like that is akin to acting in a play. The character is spelled out. Her actions are relatively clear. Her voice is predetermined. Everything about her seems perfectly normal -- except she is not a real person. Outside of that scene she does not really exist.

The loner would like to be part of something, but there is always a stumbling block, a blockade, a barrier that separates her from what she suspects reality is. Attempts to convince herself otherwise are mostly counter productive.

It is like living inside the shell of a person. Observing her from within. A lab rat watching its own reflection, missing the sensory perceptions that occur to real, non-loner types.

It is possible to live with only one long tether connecting reality to supposition. Or, perhaps, one long tether connecting to reality makes living possible.