Editing a manuscript reminds me of pruning.
Sometimes you have to cut off perfectly good branches, perfectly good characters, perfectly good scenes, so that the story can flourish.
Proper pruning enhances the beauty of almost any landscape tree and shrub, while improper pruning can ruin or greatly reduce its landscape potential. In most cases, it is better not to prune than to do it incorrectly. In nature, plants go years with little or no pruning, but man can ruin what nature has created. By using improper pruning methods healthy plants are often weakened or deformed.
So while it's important to cut our work, it's also imperative we know what we're doing.
How do you prune without ruining your work? Have you ever overedited? Took advice when you shouldn't have?