The narrator in Once Upon A Time by Nadine Gordimer is indeed a writer so is presumed to be Gordimer herself. Gordimer has received various book prizes including the Nobel Prize for literature which she received in 1991. In the story, she is expressing her dissatisfaction because she has been told that she "ought" to write a children's book. Gordimer, in her writing and her political activism, has never been one to conform, and in fact, several of her books were banned in South Africa (during Apartheid) so she would be opposed to any form of literary or other coercion.
When the story shifts to the "bedtime story," at first the reader relaxes as he reads about the family that lives "in a house, in a suburb, in a city..." and chases a dream of the "happily ever after" even though, in terms of appearances, this family already seems to have achieved perfection. However, the illusion is soon shattered when "the wise old witch" issues a warning and the reader wonders what kind of life the narrator must live if a bedtime story is as harrowing as this.
Therefore, changing from the autobiographical beginning to the ideal family draws the reader in and makes it a more personal journey for the reader. Although the story of the family is based on a sadly typical family in the suburbs of Johannesburg, South Africa in the 1980s, it has a universal quality and could relate to anyone who tries to protect himself and his family from some unknown threat. Making the shift between the real life, the imagined life and the typical life forces the reader to face his own fears,and hopefully find a better way to resolve them.