Are you participating in NaNoWriMo? It begins today and you absolutely should try it.
Whether you write a novel or a nonfiction manuscript, there is something really satisfying about a sprint to get 50k+ words down on paper in one month’s time. Consider it. But, mostly consider it because it will make you stop incessantly self-editing to the point of being unproductive; it’ll help you perfect the art of and better appreciate the reason for a good and messy draft. Indeed, the act of getting it all out of your head and down on the page is a mad dash, and the only goal of the month is to get it all down, not have it edited or make it pretty, or make sure you have no typos. So give it a try and see if a loudly ticking clock helps you get out of your own way a bit and makes you a better writer.