As so often, it feels like you've been walking around in my head. I think it's a function of being female and of a similar age & background.

I think the one thing that has helped me most with this problem was an out-and-out, indisputable failure to be perfect, a professional error that initially felt devastating. It seems perverse, but surviving that left me with a much stronger sense that I am good at what I do, that my clients respect me, and that having to say 'I'm sorry, I made a mistake' or 'I'm sorry, I don't know the answer, I'll have to check' won't destroy me or their respect.

Of course there's the years of therapy too.