The speaker goes looking for healing in the company of other people, hoping that being among them will fix something broken. It backfires. Instead of feeling better, they feel worse: the group's "beautiful company" acts like a mirror, and what it shows is "an old bag," a worn-out, sagging version of themselves. The speaker's own "ill condition" seems clearer next to everyone else's ease.
The last lines are the bluntest. Nobody, the speaker says, could make them want to exist, and they admit they don't know "the trick of trust." Calling trust a "trick" suggests that other people seem to have a skill the speaker never learned. The title, "Self-exile," points to the cruel twist: the speaker is isolated by their own inability to let anyone in, not by anyone else's rejection. The mood is bleak and quietly sad, but the plain, short phrasing makes it feel honest rather than dramatic, like someone simply stating a hard fact about themselves.