What does it mean to be effacing? (From Adams's The Education of Henry Adams)

To efface is to make oneself modestly or shyly inconspicuous.

Adams knew that he could never learn to play politics in so masterly a fashion as this: his education and his nervous system equally forbade it, although he admired all the more the impersonal faculty of the political master who could thus efface himself and his temper in the game.

From Adams's The Education of Henry Adams.