Well the lead singer (Derek) was going out with this girl names Katie. While he was away on tour Katie met this guy named Mike and she ended up cheating on Derek in every way possible. And then when he was coming home from a very stress full concert Derek knew all along that she was cheating on him and Katie finally fessed up to him about Mike. So Derek as in the song loved her so much he had to let her go so she could be happy. He knew he could live without her just would be miserable. But it was for the best of Katie.