The poem is a single sentence, and it reads like someone announcing a small victory. The speaker has spent many months getting over a person, and now, at last, they can say the feelings are gone. The title, "Thirteen," isn't explained, so it's hard to know exactly what it points to. It might be a number tied to the speaker's age, to a count of months, or to something else entirely, but the poem itself doesn't say.
What stands out is how plain the statement is. There's no anger and no dramatic farewell. The words "after many months" suggest the process was slow and probably painful, and "finally" carries a sense of relief and exhaustion. Still, the line is so short and blunt that you might wonder whether the speaker is fully convinced. Saying you've moved on is not always the same as having done it. The mood is quiet, calm and a little uncertain, like someone testing out a sentence to see if it's really true.