The light that gradually dawns on him consists in his understanding that his fantasy is a real psychic process which is happening to him personally.
Although, to a certain extent, he looks on from outside, impartially, he is also an acting and suffering figure in the drama of the psyche.
This recognition is absolutely necessary and marks an important advance.
So long as he simply looks at the pictures he is like the foolish Parsifal, who forgot to ask the vital question because he was not aware of his own participation in the action.
Then, if the flow of images ceases, next to nothing has happened even though the process is repeated a thousand times.
But if you recognize your own involvement you yourself must enter into the process with your personal reactions, just as if you were one of the fantasy figures, or rather, as if the drama being enacted before your eyes were real.
It is a psychic fact that this fantasy is happening, and it is as real as you —as a psychic entity—are real.
If this crucial operation is not carried out, all the changes are left to the flow of images, and you yourself remain unchanged.
As Dorn says, you will never make the One unless you become one yourself.
It is, however, possible that if you have a dramatic fantasy you will enter the interior world of images as a fictitious personality and thereby prevent any real participation; it may even endanger consciousness because you then become the victim of your own fantasy and succumb to the powers of the unconscious, whose dangers the analyst knows all too well.
But if you place yourself in the drama as you really are, not only does it gain in actuality but you also create, by your criticism of the fantasy, an effective counterbalance to its tendency to get out of hand.
For what is now happening is the decisive rapprochement with the unconscious.
This is where insight, the unio mentalis, begins to become real.
What you are now creating is the beginning of individuation, whose immediate goal is the experience and production of the symbol of totality. ~Carl Jung, CW 14, Para 753