One thing I have heard from some of the black belts attending my classes is that they sometimes feel like white belts again. I'm recounting this, not to blow my own horn, but to make two other points: black belts are not necessarily experts and we are all still learning.
General Choi Hong-Hi, the principle founder of Taekwon-Do and author of the ITF Encyclopaedia, was quite clear about the fact that the first degree black belt is still but a novice:
First Degree—Expert or Novice?
One of the greatest misconceptions within the martial arts is the notion that all black belt holders are experts. It is understandable that those unacquainted with the martial arts might make this equation. However, students should certainly recognize that this is not always the case. Too often, novice black belt holders advertise themselves as experts and eventually even convince themselves.
The first degree black belt holder has usually learned enough technique to defend himself against a single opponent. He can be compared to a fledgeling who has acquired enough feathers to leave the nest and fend for himself. The first degree is a starting point. The student has merely built a foundation. The job of building the house lies ahead.
The novice black belt holder will now really begin to learn technique. Now that he has mastered the alphabet, he can begin to read. Years of hard work and study await him before he can even begin to consider himself an instructor and expert.
A perceptive student will, at this stage, suddenly realize how very little he knows.
The black belt holder also enters a new era of responsibility. Though a freshman, he has entered a strong honorable fraternity of the black belt holders of the entire world; and his actions inside and outside the training hall will be carefully scrutinized. His conduct will reflect on all black belt holders and he must constantly strive to set up an example for all grader holders.
Some will certainly advance into the expert stages. However, far too many will believe the misconception and will remain in novice, mentally and technically.
ITF Encyclopaedia, Volume 1: p. 94, 95.
In my years as an instructor, one especially unfortunate thing I've noticed with some black belts is a type of thinking-they-know-it-all attitude. While the instructor is teaching a particular technique, this black belt will do another technique he or she thinks to be a better variation or will teach his or her training partner another application. Not only does it deprive the training partner the opportunity to study the techniques the instructor intends for their growth, it also deprives themselves the opportunity of rehearsing the 'basics' and having the instructor tweak their technique. The black belt may think that they are so familiar with the technique, that they have perfected it, that they need not practise it. As a 4th Dan black belt I can honestly say that I still benefit from a senior instructor checking my fundamental movements and would be very reluctant to claim to have attained perfection of a particular technique.
To really learn, we need to put our pride on a shelf and open ourselves to the possibility that we do not know everything; for only the humble can be taught. The moment you think you 'know it', is the moment you stopped yourself from learning and improving that particular skill.
Also Read: "Allowing Rank to Simplify Our World" by Joong Do Kwan Tae Kwon Do.