Within three lines the speaker has doubted her own promise. She had vowed to answer her beloved's call "with the same heart" she once gave to an earlier summons, and now she exclaims, "Lo, the vain promise!" The question that follows is anxious: can a heart "perplexed and ruffled by life's strategy" really be "the same, the same"? The rest of the sonnet answers that doubt. What stands out is that she never argues her case. In the last line she asks the listener to feel it.
The octave is a memory of childhood obedience. She recalls how she "dropped my flowers or brake off from a game, / To run and answer with the smile that came / At play last moment." The detail that matters is the smile, a leftover of play that she carries straight into duty, so that obeying is hardly different from enjoying. The syntax does the same thing. The smile "went on with me / Through my obedience," and the sentence runs over the line break just as the smile runs on through time. Her language for adult life is quite different. "Strategy" suggests tactics, calculation and wariness, and "ruffled" suggests a smooth surface disturbed. Growing up, in this picture, means acquiring complications.
The turn comes mid-line, at "When I answer now," and the grammar deliberately mirrors the childhood scene. Again she drops something and breaks away from something, but the objects have changed: "a grave thought" replaces the flowers, and "solitude" replaces the game. The adult's playthings are inward ones, and leaving them costs more. Then comes "Yet still," the hinge of the poem, and her heart "goes to thee." She interrupts herself with "ponder how," as if the idea were too large to say plainly and she needed the beloved to think it through with her. The claim itself is startling in its scale. The beloved is "Not as to a single good, but all my good!" The exclamation mark shows her feeling pushing past the sonnet's polite limits.
The form carries some of the meaning. The octave rhymes *abba abba*, and the long words "strategy" and "hastily" share their rhyme with the plainest words in the poem, "thee" and "me." The worldly and the intimate end up on the same sound. The sestet alternates two rhymes, and its last pair, "good" and "blood," is the more interesting. Together with "solitude," they are at best half-rhymes to a modern ear, which gives the ending a slightly breathless, unpolished quality that suits a speaker too moved to be tidy. The rhythm is basically iambic pentameter, but she loosens it where feeling presses. "The same, the same" has to be spoken with a double stress, like someone insisting.
The final image is the best thing in the poem. "Lay thy hand on it, best one" is a physical request, and the "it" is the heart, which can be checked by touch. Her evidence is a pulse: "no child's foot could run fast as this blood." Earlier the child ran to answer a call, but the adult stands still and all the running has gone inward. The line is made almost entirely of heavy monosyllables, so it is hard to hurry through, and it reads like a heartbeat. "Blood" also closes the poem on something bodily and alive, in contrast to the abstract "life's strategy" of the opening.
The sonnet is significant because it takes a familiar claim of love poetry, that feeling will last, and tests it against growing up. Many love poems simply announce devotion. This one admits that experience makes people guarded and then proves the admission wrong, using a measurement the beloved can take for themselves. Childhood is the standard of pure, unthinking response, and the poem claims that love can beat that standard even with an adult's burdens. Because the speaker voices her doubt first, the final claim feels earned.