I'm always reminded of a story I read from Orson Welles' daughter. Welles had dinner with her one night (he was mostly absent from her life) and she commented that her husband said she was a good writer but lacked confidence, and this was what was stopping her.

Welles derisively remarked 'Confidence? Forget confidence. If you want to write, just do a lot of it!'

I'm paraphrasing from memory, but the implication was that confidence as a prerequisite was bunk. You only get confident by doing more of it than others and realising that you're the expert now whether you like it or not. That's definitely been my experience. Every time I've been called an expert I wince because I know someone else who's better at it than me, or someone I consider more talented, or whatever. Every performance review I have is an argument with my boss where they have to reassure me I'm actually capable in my job title and among my peers. It's surreal.

I've also come to accept that marketing and pushing yourself out there is fine, as long as you don't get an unrealistic sense of your own worth. You realise there's a wide band of abilities and knowledge and you won't be able to cover them all. And that's fine. There's still value to others in putting yourself out there.