Katy perry once said that this song was about your first love, which would make since as to why this song sounds so deep, as you never forget your first love. The first verse is about the relationship and the little things that shaped it - meeting the summer after high school, making out in his mustang, getting matching tattoos, and climbing up to the roof with their parents liquor talking about what their future would be like - but they didn't plan it to end so soon, something in their relationship went wrong. In the chorus it gives us hints as to what happened - "in another life, we'd keep all our promises, i'd make you stay, so i don't have to say you were the one that got away". I think he promised her that he'd always be hers, then tried to leave her, and she let him - but later regrets doing so. Verse two refers to the fact that they used to be inseparable, and where he's at now - he's moved on (someone said you had your tatoo removed) and the realization that he has finally hit her (it's time to face to music; I'm no longer your muse).