My limited experience as a freelance technical writer and daily blogger taught me it's primordial for writers to learn how to draft fast and edit slowly.
My best posts are usually the ones I wrote the fastest. The ideas just came to me and didn't leave me bored till I was done giving birth to them.
My worst content results from a lack of time spent adjusting the structure to make it flow more fluidly, simplifying my paragraphs, and correcting my grammar. I'm sometimes too tired to care and just hit publish, hoping to come back to it later with a clearer head.
It's even more important when you are writing for a client. Increasing your drafting speed—and thus your iteration speed—without sacrificing quality makes it easier to reach a fit between your work and the client's expectations. It's also a way to increase your hourly rate if you're paid per word or piece.
As Bukowski would say, don't try. If the words won't come out, staring at a blank screen won't help. You have to do something. Anything. Make a list, draw, read, walk around. Just do something.
Learning to draft fast and developing the patience to edit slowly takes months, but the more you go through the process, the easier it will become. You just have to keep writing.