Write what you know? This is not only boring but is contradictory to the basic core of creativity, which by definition brings into being that which has not been before. If you write from what you know, if you remain slavish to the facts of what happen, you are writing out of you conscious mind and will remain stuck in the straight-jacket of you conscious perception of “reality.”
That said, there is nothing wrong with using your life or any aspect of your experiences as a jumping off point, as a doorway into the unconscious. The key is not to be slavish to the known. Rather we need to have out writer’s antenna out for the doorway into the unknown and the unseen.
Gertrude Stein put it this way: “You cannot go into the womb to form the child... What will be best in it (your writing) is what you really do not know now. If you knew it all, it would not be creation but dictation."