This particular quote seems to have passed into common usage. It’s a phrase often heard when a writer posts material for critique.
The same idea was quoted a century ago by Sir Arthur Quiller-Couch. I’ve condensed it, but you can read it in its entirety on Lisa Spangenburg’s blog here.
“Style, for example, is not—can never be—extraneous Ornament. … and if you here require a practical rule of me, I will present you with this: “Whenever you feel an impulse to perpetrate a piece of exceptionally fine writing, obey it—whole-heartedly—and delete it before sending your manuscript to press. Murder your darlings.”
Harsh words, but catchy, so the phrases have been remembered. But like many writing maxims, it’s only useful if you have some background knowledge as to what the phrase means.
I’ve read posts where writers are wondering aloud if they should cut all the parts of their manuscript they especially like and rewrite them. I’ve seen the value of any pretty language debated. So I’ll give you my take, and it’s one that I think many writers agree with.
First of all, you don’t have to kill your favorite passages just because you love them. That’s taking the idea way too far. Unless you have truly horrible taste, in which case writing is likely a losing proposition anyway, your favorite bits might be some of your best writing.
As long as they serve the rest of the story.
Many writers feel that every sentence must advance the plot or develop character. Personally, I think humorous work, like Terry Pratchett’s couldn’t survive this particular test, and I believe Sir Terry was a fine writer indeed. But his witty asides served the story. They made it richer, more three-dimensional. They were darlings that deserved to live.
If in doubt, I’d try cutting the passage, pasting it into another document, and rereading the chapter when you’ve let it sit so you can get some objective distance from it. If the story marches on without it, well and good. But if it seems like something’s missing when you reread, if the chapter as a whole is somewhat diminished, by all means put it back in.
I also highly recommend getting feedback from beta readers, and you should give their critique careful consideration. But at the end of the day, it’s your story, with your name as the author. Sometimes it’s worth it to stick to your guns. I’m afraid there’s no substitute for time and experience in making this call. Writing is an art, not a science.
As long as you’re not getting overwhelming feedback to cut a passage or phrase, if in doubt, I’d say keep it, unless it’s an obvious cliche. Sink or swim based on your unique voice.
Besides, as long as you stick with writing on a regular basis, you’ll get better. And that brings up the other option. You can always set the whole thing aside, improve in your craft, and have another look at it in six months. The answer may be obvious then.
But no matter what, keep writing.