First drafts, like first attempts at anything, can succeed, even messily. But usually they don’t. When painting, we can touch up, fix wavering lines, or paint out the whole thing white again. When writing, we can cut massive sections, or tweak phrases and words in sentences till they look better, seem more true.
It isn’t in our first attempts that we deliver our best work, or our best selves, which is really at the heart of making art of any kind. Self-discovery is an essential part of our artistic growth, and parallels our (hopefully) growing skills.
Anxiety is natural, but so is a rewrite. You’re free to change your mind and your work as it gets done and you can see it more clearly.