So I guess we could say there is two type of plateau ... a creative plateau and a physical plateau.
As for the thing you translate ... even though I could read it in English, having it in French may shed some light on something that isn't as obvious to me in English. Like a 2nd degree meaning that I may not be aware.
EDIT : Forgot to say it is always nice exchanging with you
Yes, two sides, that is the opening line of my original post;
Plateau's have two very distinct elements to them, these elements apply to all musicians.
Playing is physical and mental, it works like a see saw, one on each side.
The balance is always shifting, it should always be led by the mental side with the physical side following for the reasons I stated.