What's a non-master to make of this? While everyone certainly needs to work on tactics, positional concepts, and endgames, if you lose in the opening, what good does extensive knowledge about the rest of the game do? Surely detailed knowledge of the openings is the fastest way to success. Unfortunately, it's not.
Improving at chess is like climbing a glass mountain. You make some progress, then you slip back. You recover the lost ground, make a little more progress, and then slip back again. You improve in one area, but you weaken in another area where previously you made progress.
Your objective at the beginning of the mountain climb to chess mastery should be to become familiar with as many different types of positions as possible. You'll only do this if you expose yourself to all sorts of positions in practical play.
That's why there's a difference between what masters do and what they say. Masters have approached the top of the mountain. They've encountered thousands of typical middlegame and endgame positions. They know more about different types of positions than most players know even exist. Factors like personal style and the element of surprise start to become more important.
