We learn things painfully because a part of us has to die to fully learn the lesson.

Real learning is not additive. It is not simply adding new information to an existing self. The lessons that change behavior require the death of the belief, assumption, or identity that was wrong. That is why the most important lessons hurt. The pain is not incidental to the learning. It is the cost of releasing the previous version of the truth. What comes out the other side is not who you were, plus knowledge. It is someone new.