Told in just a few lines, the poem looks back on a relationship that seemed unbreakable. The speaker counts the time in "days, weeks, months," a list that builds slowly, as if the closeness is growing with each step. Then comes the big claim: the bond was "stronger than the biggest building you could ever imagine." It's a bold, almost childlike comparison, the kind of thing you say when you're deeply in love and certain of it.
The last line changes everything. "Together forever, right?" ends on a question, and that small "right?" suggests doubt, or a hope the speaker is clinging to. Judging by the past tense in "grew," the closeness may already be gone, and the question sounds more like disbelief than confidence. The mood is wistful and a little sad. The short lines and plenty of white space leave the reader sitting in the quiet after that question, wondering whether anything built so tall could really fall.