The speaker confesses love, and the poem is about what happens to that confession afterward. The opening line, set apart in quotation marks, feels like the moment itself: small, exposed, and final once it's said. The speaker calls these "the three strongest words," which suggests how much weight they carry. Saying them took courage, and the line "it took a while for me to say it" makes clear this wasn't impulsive. The phrase "spit it out" adds a little nervous force, as if the words had to be pushed out before bravery ran out.
Then the poem turns. The last lines, split off from the rest, tell us that something the other person did or said made those words "the most regrettable." We aren't told what happened, which leaves the hurt hanging in the air. The mood moves from hopeful and brave to bitter and disappointed. What stings most is that the speaker's honesty, the hardest part, ends up feeling like a mistake.