The speaker opens with a striking self-image: a lost horse, an animal that wanders without knowing where it is going. From there the poem admits a kind of helplessness. The speaker never sees the way alone, and doesn't quite dare to notice the plain fact of being "there / or here" while still carrying on existing.
The title, "Unmastered," adds to this. A horse without a master has no rider to steer it, and the speaker seems to have no guiding hand either, whether that means a person, a purpose, or a settled sense of self. The odd, slightly old-fashioned word "durst" makes the confession feel hesitant, almost guarded.
The mood is quiet, uneasy, and a little bewildered. Yet nothing is dramatic or panicked. The speaker simply keeps going, uncertain of place but still present. That bare persistence, in the last lines, gives the poem a faint, stubborn resilience beneath the disorientation.