To define what a person has learned and how one person has changed can be only done by people around, not own self. Frankly, this theory sounds weird but it makes sense. If one thinks that he or she has changed, it has to be seen by other people also. From what I was able to rationalized is that although he/she thought his/herself has changed, but without people around feeling it or noticing it, at the end of the day, it makes no differences. In chinese saying it's called “闭门造车”. If you are building a car without even bringing it on the road, the reliability of the car is very very low.
At the end of the day, the moral that was taught is let other people see what you have changed and how you have changed. If you think you have changed but NO ONE can notice it or feel it, it's equal to NO CHANGES. Start doing it from small things, it makes a difference.
