Writing a book is a prolonged exercise in perfectionism. One must strive for quality while resisting the urge to make it perfect. Why? Because perfection, which is highly subjective in this case, falls somewhere between unlikely and impossible to achieve. And perfectionism can lead to procrastination, writer’s block, stress, and the inability to finish one’s manuscript. Ugh!
If you don’t consider yourself to be a writer, perfectionism can prevent you from even trying to tell your story. My advice for you is to consider it a first draft that you never have to show anyone if you don’t want to. Even “real writers” start with a first draft! It won’t be perfect, but it’ll be a good start.