There's an old Zen story about an enlightened Zen master who would sit in meditation every night. About halfway through his sitting, he would shout at himself, "Don't let them fool you!" Then he'd shout, "No, Master!" It was his way of protecting himself from the addictions and the advertising messages. It was his reminder to stay upright. It was his communication with himself: by shouting to his own mind, "You can't fool me anymore!" he was acknowledging that he was the one responsible for his own purity or impurity.
— Geri Larkin, The Still Point Dhammapada