This (or a variant of it) is something that I hear regularly.
This time it was said to me by a lovely woman in her forties. She was worried about her mediumship gift, worried that she'd get it wrong, worried that she'd do more harm than good, worried she'd look daft, worried that she'd dry up. Worried.
I smiled as I asked her "So if you're so worried why do it"
"Because I have to" She replied
And this is the rub of it. Believe me I don't "know what I'm doing" not one bit of it, and every time someone comes to see me for a reading. I worry. I worry that I'll get it wrong, that I'll look stupid, that the person who is trusting me will think bad of me, worry that I will dry up. BUT I know that I have to do it.
And so I have to learn, we all have to learn, that it really isn't us that's doing it we're just available and that if "I" do it I will get it wrong. We have to learn to trust that which we're saying, and those that give it to us. I believe one way to judge a good medium is this; Do they believe they can do it, or are they trusting someone else for the information they give.
We need to stop trusting ourselves and start trusting Spirit.