The one person I knew personally who broke with reality wasn't religious, and instead seemed to be pulling ideas from her previous goals and highlights of her life. She described a sort of ideal version of her life, the best things she could think of in the moment, regardless of consistency or reality. It makes sense that if one were raised in a religious household, one would talk about being chosen by God or some such instead of how you were getting straight A's in school and getting hired by 5 different places.
She probably just wanted to calm him down and make him see the world more positive. Eventually it wasn't positive for his opponents and the world. He started to believe he has the direct connection with the God and that therefore anything he does, even the killings and tortures, were directly supported by the God. He turned out to be a "successful" prophet based on the impact he made.
https://wikiislam.net/wiki/Muhammad%27s_Just_In_Time_Revelat...
http://news.stanford.edu/2014/07/16/voices-culture-luhrmann-...
People tend to think their talking to spiritual things in some sense, but Americans heard God, or angels or demons, Indians tended to hear from ancestors or kin, Ghanaians from various spirits. Indians and Ghanaian found that many voices where helpful and positive. The Americans all found their voices to be violent and negative.