This post is very reminiscent of the book Mastery by George Leonard. He writes about the need to practice seemingly simple skills until they become natural. I got a lot out of the book; there were many sections on dealing with plateaus.
I love his breakdown of learning and teaching styles.
What I got out of the book was a realization that a good teacher will focus on the fundamentals, and will set realistic expectations.
I've noticed this and in my case it's more a matter of mindset than anything else. My day job consists of programming, and at night I do public speaking.
I find it takes me longer to get into a flow state when doing public speaking. I think the terms sometimes used are "up time" and "down time".
Practice definitely helps. I've taken improvisational acting classes and those were slightly helpful. I've learned to recognize when I feel I'm inside my own head. It feels like you know how you want to come across but actually speaking doesn't come out how you expect and you start focusing inward. The only way through it is to keep pushing yourself. Overload your senses by speaking through the situation and then volunteer to do more immediately after.
I've also found that being in a social situation when I'm internally focused will lead to fatigue, but if I take an active lead, then I get revitalized quickly.
Great post. I think this form of self-sabotage is one that many analytical people don't realize they are engaging in. As a computer programmer and a mathematician, I definitely fall into the category of analytical people.
One way I've managed to reduce this problem in my life comes from public speaking. When we give other speakers feedback, we always commend something they've done, recommend how they can improve, and finish with another commendation.
This kind of feedback is much more effective than just praise alone, which can be rejected especially in certain cultures as being unrealistic or insincere. The feedback is also more effective than pure criticism, which, as you pointed out in your post, can make the speaker hostile and therefore less likely to listen to you.