We all have doubts. In an article I wrote some years ago, I mentioned one reason writers might feel self-doubt more than others.
Everyone experiences self-doubt now and then. It’s part of being human, and writers are not exempt from this. In fact, I would go as far as to say that writers probably experience self-doubt more than other people. This is because we create things by transforming abstract ideas into concrete, readable words; and this makes us prone to criticism – whether constructive or not.
(You can read the full article here.)