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If you don't want to watch Mayer wax poetic about his failed relationship, here's just the Katy quote:
Listen, it was a very private relationship going in. It was a private relationship during and it's a private relationship, still. I can understand asking the question based on some previous answers I have given but I have finally learned how to put the wall between one thing and the other. I've been much happier since then. I'm on the same journey as everyone else. Coupling is a tricky thing.