Write what you know is something that is thrown around A LOT when one begins to talk about writing. The question I always had was, how does the average person, with a regular 9-5, write a book about cops/spies/doctors/Julius Caesar etc. if its something they weren't there personally to experience?
The answer, I found, is that 'write what you know' is more a case of 'write what you love'. Because when you write what you love it becomes a part of you, and something that you love with your entire being you know very well. Its like a comfy sweater, for lack of a better term. But, you get my point.
And when you write what you love it feeds your soul in a way that nothing else can, and you begin to feel like that missing piece of your existence has finally (finally!) been found and you can live your life to the best of your ability. Its 5 star food for the soul.
That is part of the 'mystery' of how I came to this place. Once I started to write what I love, what I really and truly love, the whole process started to feel different and who I was as a person finally began to peek out from her hiding place. Once my world began to become more comfortable that real me started making more appearances, and I started to realize that she was quite likable. And when she was happy, and her soul was fed, everything was fantastic.
So, that is my central piece of advice for anyone who wants to start the journey of writing. Trust your instincts, and write what you love, and do it with such reckless abandon it might frighten you a little. It'll show on the page, and your readers will love you for it.