I'm 45 and ~21 years into my post grad-school career. I'm finally accepting that I will probably _always_ feel like i'm failing and doing things badly and that's OK. The evidence suggests that I have in fact been doing at least a good enough job in my employers eyes to sustain a career and progress. When I look back on this evidence I don't however look at it as a list of successes, I still mostly just see the things that could have been better. But by accepting that this is just how work feels I am relieved of the stress and anxiety that feeling has caused me for two decades.