I suppose what I'm wondering is how you all change your state? How do you genuinely have unwavering belief in yourselves?
Your expectation that you need to be "unwavering" isn't realistic. It's natural for your confidence to be influenced by your mood, but if you find it disappearing in any given moment, then it's probably related to your negative self talk. I would start to look at your attachment to outcome. If you come into a room with the frame that you're open to create fun relationships with women, then all of your nonverbals will improve and you won't feel the need to hit any particular goal for that evening.
You will automatically have more appeal.
Your problem is that you're too afraid of failure and embarrassment. If you didn't have that fear, then you wouldn't be seeking confidence in yourself. You're not actually afraid of failure. You're afraid of how shitty you're gonna feel if you do fail. If your sense of well-being hinges on meeting your goals for the evening, then you're already setting yourself up for failure and feeling shitty. You're already telling women nonverbally that you need them to validate you just to feel good about yourself. I don't have to tell you have negatively that affects your game.
So the solution is to intentionally fail and get rejected so you can work through your fear of how you're gonna feel when you fail. You need to experience your own process of recovering from beating yourself up when you fail. It's all about taking action and letting go. From there you can start to self-validate based on living though those emotions enough times to know they won't kill you. And that will bring confidence without any external dependencies.