Your brilliant flash of dialogue doesn't fit. The character with the quirky personality is a dog in your aquarium instead an angel fish. You love these pieces of writing and defend them to the death. But, they don't fit!
So, you do what most people tell you: You kill them. You realize they don't work after all so you cut, set them on fire, and hit DELETE. Before you save your changes, I want you to stop. Don't get rid of them. Oh, I see your smiles now as you believe I'm ready to defend your brilliance and give you a reason to keep them in your stories. Wrong.
Hey! Hey! I say, there has to be a better way! (Overused slogan deploy!) It's true. If you recognize they don't work, don't leave them in but everything you take out, keep. Put them somewhere instead. You'll like editing more if your extra puzzle pieces shuffle into files instead of garbage bags because they still exist. Also, if you realize during a rewrite something is wrong or missing, you can go back through all material and see what ground you covered; you may find the answer or even a use for something in the file.
If those pieces don't find their way back into the project that inspired them--and few will-- they may fit somewhere else or be an inspiration for another work. A group of ideas you once thought were brilliant right at your fingertips... could be worse. Even if it is just for the prospective, imprison your darlings but do NOT kill them; you don't want to be haunted by a ghost of good writing past!
P.S. I know I touched on this subject briefly in another post but I saved a writer from a horrid mistake this week and thought I should reiterate. (I hope none of you need this post.)