"...willing to sacrifice what must be sacrificed to achieve your goal."
Want to know what the hardest thing to give up is? The one that makes people quit most frequently?
People hang onto that one tooth and nail. The hardest thing to let go of is doubt and fear, particularly to do with your ability to succeed. Doubt that you can, fear that you won't.
I think it's a crutch.
So instead of having to face "I could have done it, but I didn't" you get to say "I knew it all along, it was fate, it's not my fault, it was just something I could never have done no matter how much I tried..." or somesuch. I also think people put themselves down so it doesn't hurt so bad when someone else does. The "silly hat" defense.
Anyhow, it's the hardest thing to give up- and the thing that gets most in the way.
One thing I was taught way early on is how students are always willing to believe something bad about themselves, but may refuse to accept any praise as legitimate. Tell them they did something well and they'll almost always say "not really" or "it could have been better." Sometimes even "no it wasn't" or the currently in vogue "I suck." So part of the teaching process is to teach people how to accept positive feedback.
Trouble is, a lot of people use positive feedback dishonestly. And people catch onto that, which is why when you teach, you must NOT do that. All feedback must be legitimate, or there will be no reason for the student to trust you, ever.
And if they don't trust you, they won't believe what you say, they won't accept feedback, and if they don't accept it, it won't guide them, they won't learn, and you'll both be wasting your time.
At the same time, some positive feedback is not so much "that was perfect" as it is "that is what I wanted you to do right now" because beginners aren't going to be perfect, but they CAN take steps in the right direction. You have to be sure the student understands the cyclical nature of learning, so they can accept praise for an action as legitimate and true, even when it isn't perfect.
Accepting feedback, like anything else, takes practice.