I agree with Shadyspartan. But this song can also be interpreted to show the flaws of "love". This man is stubborn and abusive, and he knows he should not do the things he does that cause her to leave. Yet, he says a few simple words (come back to me, its almost easy) and she come crawling back, because she loves him. The definition of insanity is something along the lines of trying something multiple times expecting a different result. "I'm not insane" is saying he's not trying to change. When she finally leaves, he still doesn't change, even though he knows why she left and what he needs to do to fix it. That just shows how unhealthy it can be if the two people in a relationship don't love each other equally or aren't dedicated as much as the other partner.