Based on anecdotal evidence, most people don't believe that they have the inherit ability to write a book. How many times have I heard someone say, "I could never write a book!"?
And of the few who attempt to write a book, based on anecdotal evidence, most never finish writing their books, which, per award winning science fiction author Octavia Butler, is what, obviously, makes the difference between a writer and “I wish I was a writer.”
Octavia Butler: "I tell the students that there comes a time when you want to either burn it or flush it. But if you keep going, you know, that’s what makes you a writer instead of an “I wish I was a writer."
So, when the inevitable imposter syndrome sets in, try not to drag your doc to the trash but keep writing until your confidence inevitably returns (إِنْ شَاءَ ٱللَّٰهُ).