One piece of advice that I heard years ago really stuck with me, and it helped me out just last week. I don't remember how it was originally worded, but it came down to this: get the first draft down on paper, complete with cliches, weak description, and lack of emotion. Then go back and fix it later.
The point that came across to me is that a writer shouldn't try to make it perfect on the first draft. Because it won't be perfect. So many things will change from day one through day 365+ that if a writer polishes up each chapter before moving on, they're going to end up rewriting so many times they'll never finish the project.
I'm sure there are exceptions to this, but personally, that's how I write. I did it with my query last week. I couldn't figure out how to pitch my book on a single page, and I kept getting hung up on phrases that sounded cliche and generic. But when I "got over" that, I wrote a basic pitch and sent it off to my critique group for some review. Now I have a direction to take the query, and I have ideas that'll help me make it a solid pitch.
But if I wanted to get it "perfect" the first time around, I would've spent weeks and weeks dreading the task of writing a query letter, even when I sat down to work on it.