A lot of the editing process involves figuring out what parts of your story are actually necessary. When you're writing the first draft, it's great to just let the ideas flow and not hold yourself back from getting them out. Once you're at the editing stage, however, that's when you really need to start analyzing the story and realizing which parts need to go. This could be as small as cutting individual words or as big as whole scenes and chapters.
Every cut won't seem obvious right away. The line by line edits may be easier to deal with first. You'll know if a particular word or phrase feels awkward or just doesn't work. You may need to rewrite a sentence, or you may realize you don't need that sentence at all. Figuring out the best way to get the story across without using a lot of unnecessary or unfitting words will help to polish the overall story and make it better.
Cutting scenes and chapters won't be as easy. You may spend a lot of time trying to rewrite a scene that isn't working to finally realize you don't actually need it. The scene doesn't even need to be bad for it to be cut sometimes, either. You may have written a great scene, but as you develop your story more and more, you may realize it just doesn't fit anymore. Deciding to cut a large chunk of story can be an emotional process. You may try to rationalize keeping it, but if it isn't going to work, eventually you'll come to realize it.
Of course, cutting isn't always the only answer. Maybe you have a scene that has some necessary moments or information, but the important parts aren't quite long enough to pull off a whole scene. You may be able to move whatever information is necessary to a different scene or chapter. If you're trying to fill in a whole scene or chapter and most of it is unnecessary, it will probably slow down the story or even make it seem boring. You always want something important to be happening in order to keep the reader interested.
The realization to cut a whole chapter actually took me by surprise. Now that I'm working on the third draft of my novel, I've come to realize that my sixth chapter actually isn't necessary and slows the story down. There is definitely some important information in there, but I know I can move it to the previous chapter and still have everything go smoothly. So making this cut will help speed things up within the story, as well as getting rid of a lot of unnecessary words. Now that I know I have to squeeze in the important stuff into a shorter scene, rather than an entire chapter, I'll really have to think about what words are necessary to get the point across.
Have you ever cut a whole chapter? Or consolidated two parts into one?