We all know that voice is one of those elusive, I'll-know-it-when-I-hear-it attributes.
In my opinion, voice is innate. It slumbers in a place so deep within us that we can't access, but...and this is an important but...we can create the condition that will wake it.
What i mean by that is don't be afraid to put yourself out there along with her characters. Yes, we write fiction, and yes, our characters' fears, wants and needs aren't necessarily our own…but the want, the vulnerability, the doubts, the regrets, the passion, the pain…all comes from us, the authors.
The idea of write what you know doesn't have to do with the circumstances you're writing about--it doesn't matter if you've never been to Paris, never been a medieval warrior, never carried out a classified spy mission. What matters is that you've loved, lost, laughed and had your heart broken. Put what you know in the emotions your characters are going through.
Let go and write.