Annie's poem is about the sting of unrequited love, told by someone who has just learned that a friend doesn't feel the same way. The speaker believed the relationship was something more, and now has to face the fact that the other person only ever saw friendship. What stands out is how the speaker takes the blame. They say it isn't the friend's fault, that they should have asked sooner, and that the mistake was theirs.
Underneath that calm surface, the hurt keeps showing. "My heart is sore" is plain and honest, and the line "I don't think I can, not just as before" admits that going back to simple friendship won't be easy. Even the reassurance "I will be just fine" sounds like something said to end an awkward conversation rather than something fully believed. The steady rhyme and short, even lines add to the effect, making the speaker sound controlled and quiet. The mood is sad but gentle, a little resigned, with a lot of feeling held back.