Its definitly about a guy and his relationship with a girl. He found a girl that was different than everyone else. He asked her out and she said yes. She is the flower in the field of weeds. I think that he was using the girl for something and he changed her into something that she didn't want to be. That's the browning petals. So he let her go and let her return to the normal person that she was. He felt really bad about that and now it makes his heart burn. He realizes that he messed up and wishes that he could have a normal relationship with that person. To him that person is a figurative angel.