This is difficult, I mean in principle it is great. Use your own experience to make sense of your characters situation and you have a believable story. Except that we rarely write about our everyday lives. Instead we create lives that are more interesting, where our characters are pitched into battles, both physically and mentally, and it can all happen anywhere in time or space.
So if we only write what we know, and I take the phrase literally, it means that I would write about smallholdings and conservation, archaeology and toy-making. But I don’t, well not all the time.
Take my dissertation, that is about a female serial killer and while I may be female I have never been a killer. But I have worked in conservation, which is my main characters job, and I have handled dead animals, we eat our own produce on the farm including the meat. But these are just small glimpses in the story.
The main plot takes place on an overnight train, but I have never been on an overnight train. I have, however, been on an overnight ferry, which I found whilst researching, is very similar. Okay, so my story is not written about what I know, but it is riddled with points of reference that I have experienced; the job, the animals, the cabin. And it somehow grounds the piece.
I’ve done this with short stories as well. In one I write as a man looking back on a murder he witnessed, Oil and Water, and I’ve set it in London. I’ve never lived in London but I have lived in a city, so I reference the buildings from there. Then I used the simple action of splashing in puddles to ground the story. Running the image of oil and water through the piece allowed me to write something that I knew in almost every paragraph. I have never witnessed a murder but I use landmarks from my own life to make it seem real. The smells, sounds and images that, as children, we all have probably experienced.
So when they say write what you know, I nod sagely and take it with a pinch of salt. Seed your story with references from your past but write your story with imagination. After all, if writers took the phrase literally then everything would be an autobiography and not a work of fiction.