Writers write. Writers also read. They should read to figure out how the other guy slung words together. Writers also read about writing. We do that to procrastinate and they ought not do that. But if you stop reading here, you’ll just feel guilty, so please continue and I’ll try to make it worth your while.
“Writers Mantras” are not rules, but aphorisms. Rules have to somehow cohere in a rationale whole, but Mantras are just things found true without regard to when, where and how. You see, truth is complicated, and truths about writing have exceptions, and exceptions to exceptions, /et cetera ad infinitum/.
Here’s the first Writing Mantra I found: “Work your opening paragraph to death.”
Let’s suppose your best prose is in your second paragraph, but your reader (a book buyer or an editor) never sees it, because s/he tossed it after reading the first paragraph. You’ve got to set the hook and reel in your reader over the course of the rest of your novel.
The last thing you want is for your prose to get tossed into the slush pile or put back on the bookshelf because of some goof in the first paragraph. You’ve got three pages’ of prose to convince the reader to commit to reading your work.
You want a trust relationship with your reader. Your story should raise questions in your reader’s mind. “Read more and I’ll give you answers.” Then you need to give satisfactory answers. If you are smart the answers will be such that they raise larger questions in your reader’s mind. This keeps the reader turning pages until you conclude the penultimate chapter.
The last chapter is where you sell your next novel, but that’s another story.