Everyone seems to be pushing confidence. In the world of hypnosis and in life in general. It gets people so focused on projecting that they know what they're doing that they try to delude themselves into believing it. "fake it until you make it". That can actually be helpful in some cases, but in other cases it either doesn't work or worse. I've even seen it go as far as posting on the hypnosis forums about how amazing you are in misplaced hopes that it would give you the confidence to succeed - though I somewhat doubt the kid ever even tried. There's definitely something important there, but "confidence" misses the mark.
Okay, so lets dig into it. Remembering that people leak, what are we really suggesting, when we break it down? Take a typical beginner. He ends up suggesting that he doesn't know if it's going to work, they focus on that, it doesn't work. Now look at an expert. He's done it enough that he knows it'll work - and so they focus on that and it works. It must be the confidence! But I can't be confident until I see it work! What a vicious cycle! I must try to fake it til I make it!
Well, that's the standard narrative anyway. It's missing a few key bits. One important one is that the expert has actual skills too. Skills in calibration so he knows where they're at, and skills in navigation so he knows how to lead them from there. More on topic though, is that there is a big difference between not being certain it will work and implicitly suggesting failure. Remember, it's all about where you aim their focus. Their focus follows yours. If you focus on it not working, they will too. So simply acknowledge the possibility of failure. Hang a lampshade on it and move on. That's it.
"Hey, can you try an experiment with me? I'm not sure what will happen and I'm really curious"
"I NEVER fail. In fact, you're already hypnotized by my greatness! You're stuck to the ground! Try to move and fail!"
So much confidence, how could that possibly fail? Well, people leak. It comes off like he's trying to convince you, so you direct attention to what he's trying to hide - the possibility of failure - and it fails. And then he's SOL. He's lost all credibility by sticking his neck out without enough calibration to know it's not getting chopped off. If hypnosis is powered by magic confidence juice and it doesn't work with the most you can throw in there... then you have nowhere to go from there.
If instead, hypnosis is just skillfully navigating thoughts, then when something doesn't work, you know where to go from there - and confidence isn't an issue because you aren't focusing on failure so why should they. Of course, you can get stuck and you can't figure out how to navigate this one. That's where owning failures comes in. Lampshade it and move on.
The problem with "lacking confidence" fundamentally comes from trying to oversell things and the fear of getting caught out as being in over your head. So don't get in over your head. And still go forth.
If you aren't confident that it will work, confidently own it. You can be confident that it's worth trying anyway - or what the heck are you doing?
Or hell, maybe you aren't. Maybe you still think hypnosis is actually new age/pseudoscientific bullshit. Lampshade that. Be confident that you're going to try it anyway and find out. After all, the brilliant badass Richard Feynman was a genuine skeptic of hypnosis, but he went into it intending to see what it's all about - and surprise surprise, it worked.
What aren't you sure about? Acknowledge it and move on. What are you sure about? Own your confidence in that.