If writers produce good copy, whether for a book, an article or a website, it’s probably because they spend more time editing and polishing their draft, and less time writing it.
A draft should be written quickly, as fast as possible. It needn’t be very good; in fact it shouldn’t be. If you try to write perfect sentences straight away, you’ll waste time editing and correcting as you go and may lose the thread of what you want to say.
I’m assuming you’ve thought about your subject and planned what you want to say. If you have, once you’ve got your thoughts down in a rough draft, you can stop worrying about when you’ll finish the piece and spend time improving it. It’s difficult to resist editing as you write, but it works.
I find this process makes writing not just more efficient but more fun. Writing is a chore; but thinking and planning before, and editing and polishing after, are enjoyable.
If you’d like to read more on this approach to writing, have a look at an article by a writing coach I follow, Daphne Gray-Grant. It’s called “The joy of the crappy first draft“.