According to Sai Baba, what is the prerequisite for him to personally author his own story through a devotee?

According to the teachings in Chapter 2, Sai Baba states that the devotee must first dissolve their ego and surrender it completely at his feet. He explains, "He should dissolve his ego and surrender it at my feet. To one who acts thus in life, I give full assistance." Only when the ego is gone without a trace does Sai Baba promise to enter with his own 'I-ness' and write the story with his own hand. In this divine process, the human author becomes merely a pretext for the work that is truly being accomplished by the One to whom it belongs.