The speaker is trying to get over someone who moved on without a second thought. The poem opens with a plain, firm statement of need: "I need to forget about you." The next line explains the hurt behind it. The speaker was forgotten, and now wants to do the same in return.
Notice how often the word "need" carries the weight. The speaker isn't saying "I have forgotten you" but "I need to," which suggests the feeling hasn't quite been settled yet. The calm, short lines sound determined, but the effort shows through.
The ending turns to a book metaphor. The speaker was only "a page" in the other person's story, while that person was "a chapter" in theirs. It's a quiet admission that the loss weighed more on one side. Still, the final claim, "I will be fine," gives the mood a sad but steady strength, like someone talking themselves toward moving on.