The speaker is afraid of the word "forever." It sounds scary, and they admit they wouldn't know how to react if someone said it to them. Their first instinct would be to push it away, put themselves down, change the subject, or simply leave. That tells us the speaker doesn't quite believe they deserve a promise that big.
The middle of the poem turns to a painful memory. The speaker once asked, "If I died what would you do?" and the other person changed the subject. Now they can't stop wondering why. Was it that the person didn't want to answer, or that they couldn't, because the true answer wasn't something they could say? The questions pile up without relief.
The mood is anxious, vulnerable and unsure. The ending is the most striking part: the speaker begs for honesty but rules out the easy, comforting answer. They would rather have a real answer than a pretty one.