Among the best advice I’ve received on writing is the admonition to give yourself permission to “Write a shi—y first draft.”  I believe it was Stephen King’s advice in On Writing, but it could have been Anne Lamott (whose Bird by Bird is a wonderfully entertaining discourse on the writing process, authors, and publishing – highly recommended).  The point being, you should plow through to the end.  Don’t spend hours or days polishing and re-working chapter five, because when your first draft is finished, chapter five may not fit at all. As difficult as it is to delete a full chapter, or more, it’s a kindness to your readers.  If it doesn’t advance the story, let it go.