"Entertaining an idea or indulging a fantasy that you are a skilled manipulator is wildly different from deceiving yourself into believing it. "

Distinguishable, yes - but as far as much of our minds are concerned, there is no difference. They tend to treat an imagined or hypothetical scenario as though it were actual data and actual conclusions - and the more clearly the situation is envisioned, the more strongly the pseudobeliefs are held, the more powerfully they'll respond.

People tend to become what they pretend to be. The longer and more intensively the pretense is maintained, the more likely they'll come to believe it themselves.

Remember, too, that we derive our ideas about ourselves by observing our own actions and then making up stories to account for them. If you can induce people to act as though they believed something, they'll tend to conclude that they believe it, and act accordingly in the future.