Some writers craft each sentence, paragraph, scene, and chapter as if they are a Swiss watchmaker. And when they get to the end, a quick polish and the book might be ready to be shown to someone else. Hey, if that works for you, great.
I’m not like that. Writing a book explores how your characters react to each other and the world. Writing a plot tests it for coherence, probability, and interest. Writing your ideas may shift how much you want to emphasise one thing or another, or begin to strengthen and draw out themes that were not explicit in any plan.
I think that would be true even if you plan chapter by chapter in advance.
There is every reason to believe your first draft will need at least one major revision, at the level of character and structure. Probably more than one. So it feels to me that aiming for it to be perfect as you go is a mistake.
I am 30,000 words into Mysterious Second Book, and already I have lists of things I want to add, strengthen and possibly remove. I have a choice, to go back and redo what I’ve already done, or keep ploughing on, taking notes. I’m also leaving scenes that aren’t working to come back to them.
If I must be happy with everything I have written, and I must write everything I need up to this point, I could hover for months endlessly refining. I could get stuck on a scene I may decide in the end I don’t need. Better to have the whole thing done, however patchy in places, and then know what you are working with.
So, when someone says the first draft can be crappy, they don’t mean that bad writing is good, that everything in it ought to aim to be crappy. They don’t mean, in my experience, that they don’t read each chapter over and fix or annotate obvious issues. They’re saying, they have let go of what they have written first off needing to good enough to show. It will be the second or third draft, perhaps, that might be fit to be let into the light.
The most important writing advice is probably read a lot. The second might be, don’t do what Famous Author says they do just because they say so. Understand why they do it. Maybe, you should try it, maybe you should accept it, maybe it is the best advice for you ever. Maybe, you will end up like other authors who don’t do that.
What you don’t need is a folder full of the first thirds of several different novels, each polished to gleam and yet abandoned.