Vomit on the page because you can always mop up the yucky stuff and no one will know. Get the material written. Let it flow. That's the first draft.
Don’t worry about syntax, grammar, or consistency: just write. I recommend that you not edit yourself during the first draft. Novice writers often bog down because they try to make every sentence perfect before they can go on to the next. Resist that urge to make it perfect in the first draft. In this computer age, you can make changes easily, and no one else will know how much you edited.
In my early days of writing, I had to fight that urge to make each paragraph totally right, and I realized how it choked my thoughts. I began to say to myself, "I write creatively; I edit analytically." That means I wrote, wrote, wrote. After I finished an article (or a book), I went back to repair the bad spots.
A few times my personal critic grumbled as I zoomed ahead. I started talking to that negative voice. "Relax. Let me write it. After that, you can tear it up as much as you want." That worked for me.
I've been at the craft a long time and my tactics have changed. I often do minor editing as I write. I can do that and stay at my task, but that's the kind of self-discipline most of us have to learn.
Write the first draft and allow no distractions. Afterward, you can make improvements.