The structure of Wyayy's poem, in iambic (x/) trimeter (three metric feet x/ x/ x/), is four sestets in am atypical rhyme scheme of a b b b a c, with subsequent stanzas replacing /b/ with /d, e, f/ respectively. A typical Wyatt sestet rhyme is a b b a b b.
The first line repeats at the beginning of each stanza with no variation to "And will yhou leave me thus?" except for a change in punctuation from a question mark to a comma in stanzas 2, 3, and 4. The same line repeats as the fifth line of each stanza with one variation of "As for to leave me thus?" in stanza 2. The sixth line of each, with no variation of word or punctuation, is the emphatic "Say nay, say nay!"
The theme is the poetic speaker's appeal to his beloved to refrain frpom leaving him; the appeal is posed as a series of questions that ask about "shame" and "blame"; that assert past unvarying love through "wealth and woe and wrong?"; and that remind of a heart given "from you not to part" from "him that has loved you ...." Of course, the speaker ends his appeal in each stanza with the pleading "Say nay, say nay!" with no variations.
The predominant literary device is the asking of rhetorical questions such as "And have no more rue / For him that has loved you?" A repeated literary device is a figure of speech that is a word scheme called diacope, which is the re[petition of a single word or phrase as in "Say nay, say nay!" While sensory imagery like "O dear, you run me through!" is limited, strong vocabulary words evocative of important abstract concepts, like fidelity ("That has loved you so long") and innocence, which is opposite of blame ("To save you from the blame / Of all my grief ...") are used throughout.