The meaning is really obvious... He was in love with a girl who was 'lost and broken' and she ended up cheating one him ('Now it's a shame you've lost your touch and you can't control your lust.') He wanted to forgive her ('I was only a heartbeat away from forgiving you') but she cheated on him again or was unrepentant and so he decided to 'let the past be' because it was obviously over with this girl. At least thats what it sounds like to me...
The meaning is really obvious... He was in love with a girl who was 'lost and broken' and she ended up cheating one him ('Now it's a shame you've lost your touch and you can't control your lust.') He wanted to forgive her ('I was only a heartbeat away from forgiving you') but she cheated on him again or was unrepentant and so he decided to 'let the past be' because it was obviously over with this girl. At least thats what it sounds like to me...