Annie Lamont talks about writing a “shitty first draft.”
A good first rule in writing is first make a mess, then clean it up (William G. Perry, Jr.) Creating the mess allows your unconscious to work, where writing a good draft right away arrives dead-on-arrival from the top of your head.
Also if you throw in everything and the kitchen sink you will discover the novel’s shortcomings: what characters don’t work, what scenes add nothing to the novel, doubts you may have about the structure or the order of the scenes.
So, if you want to avoid writer’s block, have the courage to write the ‘shitty first draft” and then find the discipline to clear it up. Otherwise you are using one side of your brain and you risk creating writer’s block by demanding too much of yourself from the beginning.