Some writers (mostly novices) fall in love with every word they write, and find it hard to part with their prose, so much so that I advise that you get a sample edit.
Thereafter, if you can see an improvement from the editor’s work, for example, the words flow better, sentences are crisp and your writing has more clarity, then you should be happy.
If, however, you don’t agree with the kinds of changes made, you need to discuss your concerns up front and come to an understanding, whether it is that the editor is not a right fit for you, or you get clarity and agree as to why his or her editorial changes will make your manuscript more salable.
It’s important you feel comfortable working with your editor. She/he knows the rules of editing (you should have researched credentials), but if you feel strongly about something, it is your book and you have the last word.
Bear in mind though that some editors may pass on a project if you go against their expert opinion.