This quote by Wilhelm Steinitz suggests that chess is a game that needs a certain level of nerve and decision. It suggests that those who are timid or lack confidence may not be fit to the game. Steinitz is recommending that chess is a video game of strategy and skill, and that it requires a certain level of boldness and risk-taking in order to succeed. He is likewise suggesting that those who are shy might not be able to deal with the pressure of the game, or the potential for failure. This quote is a tip that chess is a game that needs a particular level of nerve and decision, which those who are shy may not be fit to the video game.
"Seem to be telling this, but really telling that. Three-dimensional writing, like three-dimensional chess. Nabokov was the other master of that. You could learn something from Nabokov on every page he ever wrote"