The poem begins with several mysterious, seemingly paradoxical statements. The speaker claims to "have walked through many lives, / some of them my own," and adds that "I am not who I was." What could it mean to have experienced multiple lifetimes—only some of which were yours—and not to be your former self after you've lived through them?
The speaker isn't some sort of supernatural entity who's been reincarnated and remembers past lives. Instead, these statements are metaphorical descriptions of aging (written by a poet in his 70s). This is a speaker who's old, weary, and experienced enough to feel as if he's lived multiple lifetimes. He now feels like a completely different person than he used to be, so some of his past identities at least seem to belong to other people. In any case, he's lost "who [he] was" originally. Right away, these lines establish transformation and loss as key themes of the poem.
They also establish a pattern of short, free verse lines that will continue throughout the poem: the line lengths will vary, but they'll never exceed eight syllables or drop below three. As a result, the poem's pace is slow and marked by frequent pauses—appropriate for an elderly, tired speaker.
The word "walked" (line 1) is another important detail: as the poem takes shape, it becomes clear that the speaker is journeying by foot through a desolate landscape. But this landscape is charged with symbolism, suggesting that his journey is more symbolic than literal. What does it represent? The word "lives" (line 1) is another early clue. The poem traces the journey of life itself—or, rather, the plural lives people seem to pass through if they're lucky to survive long enough.