My ultimate goal as an editor is to make sure that the story you are trying to tell, or the message you are trying to convey, is done so in the cleanest and most understandable way possible.
You, as the writer and expert, have a very different viewpoint on your work than I do. I am an objective reader. I am your audience. If I don't understand what you are saying, neither will your potential readers.
As your editor, I need to be honest with you. Don't ever take it personally. If something stinks, it's not an indictment against who you are, simply an observation from the mindset of your potential readers. Don't worry - I've written infinitely more crap over the years than stuff worth publishing.