Blue Balloons is about the aftermath of a relationship ending, told by a speaker who is still hurt and still hasn't let go. The opening lines set the tone: the speaker hoped the other person wouldn't change, but they had already moved on, "on the other side of the page." Even the sky, which should be perfect, looks grey. The speaker pins the pain to one exact day, the 19th of May, as if it's been replayed many times since.
The feelings are mixed. There's heartbreak and a sense of being abandoned, but also a flat, defeated honesty in lines like "I'm not afraid of losing you anymore." In the last stanza the speaker dresses to make the ex jealous and admits to becoming rebellious, which suggests anger and a need to be noticed. Friends say it isn't worth it, yet the speaker keeps returning to the promise "we'd never quit." The mood is sad, bitter, and a little stubborn, with hurt sitting just under the defiance.