Don’t swallow your words before they reach the keyboard.
First drafts are supposed to be riddled with scattered thoughts. You are supposed to let it all out and organize it later. When we don’t allow our minds the space to unload, we lose that connection to our creativity. There’s writers out there writing entire novels and still starving for creativity. Letting your mind wander is one of the most important aspects to creativity and inspiration. That is exactly the place for your first draft or even your writing journal.
Don’t stifle your creativity while doing creative work. Let it flow. Let it happen.