You should write what you really know — as opposed to a slick, bowdlerized version of what you know… For most writers, it actually takes a lot of hard work and many false starts before they are in a position to extract what is most valuable and interesting form their autobiographies.
It may be that the DNA of fiction is, like our own DNA, a double helix, a two-stranded beast. One strand is born of what writers have experienced. The other is born of what writers wish experience, of the impulse to write in order to know.
For me, writing is like a circle. I started writing about people I hadn’t met and lives I hadn’t experienced, but the stories I came up with all went back to my own perception and observation of the world, in other words, what I know about the world.
For example, I wrote some stories about love. The characters were different, from high school students to migrant workers, but when two characters started to interact in my stories, one of them would keep quite silent, and the other one would be wondering all the time. This surprised me because I hadn’t thought I might write the same story again and again in different ways, and this was also frustrating because I didn’t know if I could write another story. So I thought about it, then I realized it was just the way I perceived love. Love is mystery.
So, it is not a choice for writers to choose whether they should write what know or write what they want to know, but a fact that what they know eventually defines what they write.