I can't write effortlessly or perfectly. I must sweat over the process of revision, drafting, and redrafting until I get it right. I think most people are the same.
Very few people think clearly enough to communicate what they mean. Ideas rarely form exactly how you imagine them. We revise our words and refine our thoughts all the time, making small improvements in our thinking and presentation.
Writing is the process of discovery of our ideas. Writing is refined thinking.
I am writing for myself. I am thinking out loud. I write to discover what I know and gain clarity through articulation.
Some of my worthy ideas, I only thought of when I sat down to write. That's why I want to write; to get more of them.