“I’m an imposter. If they knew what I knew I’d never work again.”
This may be true. If it is, you’ve got some work to do. (Even if it isn’t you’ve got work to do anyway).
At the same time it’s worth bearing in mind that you don’t know what they know or see what they see. It’s possible that as you tell them your story of weakness, failure and inadequacy they’ll tell you a story – your story – of perseverance in the face of adversity; of hard choices faced and impossible decisions made; of good intentions and actual kindness.
It probably helps you to be hard on yourself. But if you knew what they know – about you and about themselves – you might find reasons to be kind to yourself too.