Dealing with insecurities like this is a very individual process, and so I don’t want to be presumptive and act like I have all the answers. But if it helps, every author I’ve ever known has had these same feelings. I was so worried about it at first that I didn’t even tell my roommates—my very best friends—that I was writing books until I’d already finished three.
For me, the transformation happened slowly. But the more I wrote, the more confident I became—not in the writing itself, but in my enjoyment of it. In those early years, it mattered less and less what others thought, as I wasn’t writing the stories for them. I was writing because of the pure enjoyment I got from creation.
Putting this first made me much more able to accept the idea that people would be critical of my work—because that was secondary, like someone looking over my shoulder and commenting on my choice of dinners. If I’m enjoying the feast, what does it matter what someone else thinks of how I’m cutting the food?
As I said, this is individual. But my advice: Don’t treat the book or story you’re working on as the main product of your time writing. Instead, look at your enjoyment, fulfillment, and progress as a writer as the primary reasons you write.