Save your scraps
You never know when you’ll want them back.
When you're writing, get in the habit of saving the pieces you cut—lines of dialogue, bits of action and description, or entire paragraphs and chapters. Put them at the bottom of the page or in another file.
You may never use them, but it's always nice to have them saved somewhere for the possibility you need them later. It allows you to go back and find that favourite phrasing or fun back-and-forth between your characters.
Same thing with drafts. If you ever feel like the writing is going in a different direction or you're making significant changes to the piece you are working on, save a copy, label it as a new version and move on.
I do this often when writing stories and these blog posts. I'll do a clunky first draft, with free-writing and failed beginnings, then save it as a v2 before rewriting or proofreading it. Depending on the day, I may end up with three or four versions before it is finished.
Again, you may never use it, but it's always nice to have it in case you do. And if anything, it's a lovely record of your writing growing to fruition.