Your voice
I was worried at first when I started my personal blog. I knew that all my friends and family would be reading it. How would I write a blog post so that it would be suitable for both my grandmother and my long time friends?
I was even more worried when I started this blog. I was going to have some kind of professional persona on top of my personal persona. Now my friends and family could read this site, and strangers and colleagues could read my personal site. How could I possibly express myself consistently to such a wide range of people?!
Well, it turned out to be not a big deal at all. It forced me to do something pretty great: it forced me to be myself. It forced me to be honest and transparent. I can't pretend to be something I'm not, because anybody can call me on it. Not on this site, nor on my personal site.
It took some time to get used to it, I suppose. I shared some things on my personal site I wouldn't normally share with everyone, but afterwards it was totally normal. I've also expressed ideas on here I wouldn't normally talk about with friends and family and I'm glad I've done it.
So when people tell you to "find your voice" when writing, they're not suggesting you try to create a brand new voice. Instead, you need to find your voice, the one true voice inside you, and share it with the world.