When my son went to Karate classes, the instructor had a belt that had once been black but was now practically threadbare. Most of the black threads had worn away, and the belt was almost white again.
The instructor explained that this represented a cycle - even the most experienced black belt needed to return to the basics, needed humility and the desire to learn, needed to always think like a beginner rather than strutting around arrogantly like an expert. So there is an important meme here - the black belt becomes a white belt again.
The same is true of management best practices. There are people who proudly call themselves "Black Belt" in various disciplines, such as Six Sigma. Perhaps they too need to become White Belts again?
See also Mike Selvon, From White Belt to Black Belt
and Vineet Nayar, When was the last time you de-learned?