Music is actually a dangerous drug when editing. Music trumps visuals. If you have a happy shot but put sad music on it, the music won't be colored by the picture, but the other way around. Ergo, putting finished, polished music on an edit makes the sequence feel more complete than it might be. What you should do is try to get as much of the emotion out of the scene by the editing choices. Typically, music should only be added AFTER you've got an edit that works.