Time for me to be a shill.
One of the writing professionals I follow is Joanna Penn, who has paid her dues, worked her way from beginner to established author, and built a website filled with helpful resources.
Here is a link to her YouTube video, How to Deal with Self-Doubt As A Writer.
Here is a link to an excerpt from her book, The Successful Author Mindset.
A few of the quotes:
“Bad writers tend to have self-confidence, while the good ones tend to have self-doubt.”
I’m tired, disappointed, wondering what the hell I’m doing with my time.” –from Joanna Penn’s journal