When I was a younger writer, a common bit of advice I got was to just run through your first draft without worrying about editing. Crafting the story, as well as crafting the words, comes in subsequent drafts.
I disagreed with that advice. I would always say that I edited as I wrote my first draft, which saved me from having to write subsequent drafts. I thought I was special.
For one thing, I was wrong. No matter how hard you work on your first draft, it will always be a first draft, and will need a ton of work, often including a complete rewrite. You end up saving a great deal of time by just plowing through that first draft to uncover the story, then doing it again to develop the story.
For another thing, I have come to realize that I wasn't special. Every person I have talked with on this subject tells me the same thing. They edit as they write. They don't just spew words without thinking about them or fixing little mistakes as they arise.
Few truly spew. Writing is a careful thing. The people who wish to put effort in their writing will be doing so from the beginning.
I don't think it is a bad thing to be careful. Although the idea of just spitting out words and not looking back until you reach the end is interesting, there is a part of me that needs to fix the spelling, needs to work on wording, wants to get a scene feeling right. I have learned to let go. I have learned that some things you can leave for later, especially if you know you are just going to scrap the words and rewrite it later. And I think that's really the crucial part of the first draft process, anyway,