Hence he is self-conscious all the time lest he make a slip, contradict himself, lose the result he is seeking to attain.

He is to be compared to an actor whose part requires him to wear a wig, a false moustache, a false chin.

In the hurry of preparation these shams are not adjusted properly and the actor rushes on the stage fearful every moment lest his wig is awry, his moustache fall off, or the chin slip aside and make him ridiculous.

He dare not stop to make sure, to "fix" them if they are wrong, as that would reveal their falsity immediately.

He can only play on, sweating blood the while.
In the case of the actor one can laugh at the temporary fear and worry, but what a truly pitiable object is the man, the woman, whose whole life is one dread worry lest his, her, false appearance be discovered.