I'm coming at this both as a teacher and from some experiences I've had as an adult music student. I have concluded that the most important thing for a teacher to do is to give a student skills so that the student becomes competent in what he or she is learning. When that happens a lot of other things fall into place, such as a student's lack of confidence or lack of self-esteem. Rather than addressing the "psychology" of a student or going after "behaviour modification", check first if you are passing on skills and know how to do so.
Being able to create skills is not that easy. The teacher has to know the subject inside out, and know how to teach it. It is not good enough to have mastered it yourself. A talented pianist might have the hardest time teaching things that came naturally to him as a child, because he never had to think about it and so doesn't know how to break it down and transmit it. A student who flounders and feels stupid will not be getting self-esteem.
I'd say that there are two stages to learning to play (or learning anything). The first is to get the building blocks. That includes every basic concept from knowing where the notes are, that there are notes, sitting and moving, reading, to knowing how to practice, how to approach a piece, and knowing how to work with a teacher. These are very powerful things and not always valued enough. The other element is the artistic side of interpreting music, making the music come alive and become beautiful. Some teachers who excel at the second are not that good at the first. The concert performer who gets a beginner may fail at giving the building blocks, and not understand why his student is struggling.
Our society also gets in the way. Kids are pushed into lessons against their will by parents who have odd reasons. Institutions forcing grade systems and competitiveness to "motivate" and in general interfere with a good teacher wanting to do his job. Being forced to go toward false goals to please examiners or judges, or to up the student one notch each year in "grade levels". Demanding parents demanding the wrong thing, judgmental peers, students of all ages being damaged by previous teachers or authority figures, or overwhelmed with schoolwork. These are part of a teacher's realities.
Finally back to the bland beginning. If a teacher does these things, then to me this is an idealism. I am leery about a certain kind of "idealism" because I've seen a kind that creates a lot of harm. I've encountered a few evangelical pop psychology types who go after students' personas, where I think that if you want to change attitude, make sure you are giving skills and a lot of that will fix itself. And then I had one encounter with a science teacher when my child was in high school. My son was disgusted that this teacher had not bothered reading the text that she was teaching, violated safety rules, had not mastered her subject. He was afraid of opening his mouth in case something sarcastic came out because it infuriated him. During a parent-teacher interview she played psychologist, wanting to know how to "draw out" my son who she saw as a troubled youngster unable to make friends (he had plenty!) - I had to restrain myself from saying "Go home. Study the material you are teaching. Learn the safety rules posted in your classroom and follow them. Earn your students' respect by being competent!"
Finally, Yehudi Menuhin said that if you have not harmed a student, then you have already done great teaching.