There is a saying in editing that you must be willing to ‘slay your babies’. In other words, you must be willing to cut out very good (or even great) material that you love if that material does not serve the story. Sometimes, no matter how good a certain scene or moment is, if it does not help propel the piece forward it ends up on the cutting room floor. Recognizing when this needs to happen, and actually doing it, is one of the most difficult aspects of editing.
Though much less talked about the converse is also true. There are times when you have to make a bad edit, or leave a bad shot in, because that is the only way for the scene to play out. Maybe the actor never nailed a solid take, there was insufficient coverage or there were technical difficulties during production. Whatever the case maybe you, the editor, are hampered by someone else’s mistakes and must make do.
You stare at the screen, pondering how to get the garbage out of your cut. You experiment by doing a little trimming here and a little rearranging there but to no avail. The edit, as a whole, is better with the garbage in it. As much as it pains you to admit defeat the garbage must stay in order for the cut to work. No matter how nicely you dress it up (even if you receive genuine compliments) you will always see a fractured edit that will never live up to your idea of how fine a piece it could have been.
This is what I mean by the politics of a cut. It is the constant push and pull, negotiation and compromise between what the editor wants and what the footage is willing to give.