One often repeated tip for those working on a first draft: Just write the whole thing; don't revise at all until it's done. This makes sense to me. Many writers get hung up on the first chapter, page or paragraph, thinking they can't go on until they get it just right. Which it never really is, and that keeps the writer from moving forward with the story.
The flip side of this is the many writers that say the first thing they do at every writing session is to re-read the last chapter, page or paragraph they wrote to get them back into the story. (And who can re-read without editing just a little?)
This also makes sense to me and I personally recommend this practice to others. It really does help you remember where you were and where you were going. But if you find any big problems with what's already written, instead of stopping your momentum to fix it, make a note and continue with the narrative.
Like all advice on writing, whether it's about style, plotting, characterization, process - whatever - do what works best for you. If you come across something that might work for you, try it and see.
(For the one bit of writerly advice that I have rarely heard refuted, see my post "To Write Or Not.")