I really liked this! Most people that write songfics somehow manage to screw it up, but you didn't. :)
The length seemed good for a songfic: not too short, and not drawn out too long either. I liked the use of the game flashback to show just why Luna is so distraught at this point in time. And the emotions displayed just felt so real to me.
So overall, I think you did a great job. :) Keep writing more fanfics!