Cutting sentences, paragraphs, or even chapters from your novel can be a painful process, but it doesn't have to be. I kept hearing the advice that I needed to cut the prologue from my novel because~according to agents and editors dishing out the advice~no one reads prologues anymore. I disagreed, fought against the advice, and probably got more than a few rejections because of it. Finally I caved and deleted it, but I discovered a way to keep it relatively painless. I'm not saying you should or shouldn't delete prologues because I still love them both as a reader and a writer, but the deleting part is easier for me now.
Tip: Keep a file of all the things you delete that you'd rather not, or think might come in handy later. Here's the real gem in the tip; you can use deleted chapters or prologues later as promotional material released on your blog or website.