How do you deal with imposter syndrome?

I've been writing a while now, sold a couple of scripts to TV and have been able to live off my screenwriting for the last couple of years now so far. I'm very thankful for that.
So I guess I'm confident to say that I know how to write a script - at least good enough to get some people to pay me for it.

But the more I write, the less I think of my writing. Dunning-Kruger effect in action, I guess.
And with every new project that I start, the beginning is the same:
"What the fuck am I even doing here? I don't know how to write."
These thoughts often go to the extent that they actually become crippling.
After some time with the story, they get less and less. But the start ist an ordeal sometimes.

Does anyone else have these thoughts at the start of their projects? How do you deal with them?