As a teacher, I can't tell you how many times I watched my students agonize over their writing. They expected the first thing they wrote to be quality work, worthy of turning-in. No matter how much I emphasized that writing is a process, that it takes rewriting and revision and editing, they took it as a personal failure to see any comments or remarks from me - their teacher - that would improve their writing.
I know their pain. My current WIP is the first thing I've produced that I would characterize as being even remotely "editable." Meaning, the writing isn't always great, but for the first time, I've plotted it well enough that what I'm tweaking is internal vs. external dialogue, or tightening 3rd person limited POV. Every plot point in the text pushes the story forward and my characters are well-rounded. I'm focusing on writing techniques within the text - foreshadowing, imagery, humor. Yes, I'm also plugging plot holes and strengthening characters, but the fundamental story is strong, enabling me to strengthen other aspects of the novel.
My wonderful husband saw these articles about Kazuo Ishiguro and Sitzfleish, and I can honestly say, my Sitzfleish is world building. It's important in a high fantasy novel to have a well-thought out world, but for me the initial writing of that world is... well, let's just say only a few key elements from the first drafts will ever make it into the final draft of the story.
We must give ourselves permission to be terrible, horrible, awful writers. Writing is, after all, a process. Sometimes, the job at hand is creating a world. Or creating believable characters. Or tightening a plot. And I'm humbly reminded that the first thing out of my fingertips, on the keyboard, need not be "my best." That will come later.