Being a writer= writing things

Being a 'good' writer = writing things for the enjoyment of others

Being a professional writer = Being paid to write things (no matter how few times)

Being a full time professional writer = Doing nothing else but writing.

See where you are on the list and keep moving up. Everyone has imposter syndrome, I sure do. I blundered into a career as a writer and quickly realised that absolutely nobody knows what they're doing. 12 publishers turned down Harry Potter.

Once you accept the world is comprised of giant children pretending they know what they're doing solely for the benefit of other people, you'll feel much better. It isn't about self belief - it's about not interpreting the cluelessness of other people as profound.

Forge your own path and keep on keeping on.