When I was little, I would get so frustrated when I tried to write something and it just didn't work out. And I often blamed this on my parents.
Was it their fault that I didn't plot out story lines so I would know what had to happen next? Was it their fault my characters and scenarios were so cliche they bordered on absurd? Was it their fault I had little to no will power when it came to sticking to one story?
No. No, it wasn't.
But even at the tender age of eight, I had heard the phrase "Write what you know!" so many times, that I believed I could only write truthfully about things that had happened to me, or people I knew. So I blamed my parents for giving me such a happy, fulfilling, even generic childhood. Sure, it had its bad times, but I wasn't raised by wolves or the abandoned child of royalty (I look far too much like both my parents for this to be true).
I blamed them for robbing me of my possible stories.
And then I read some books on writing, and I went to a summer camp for young writers, and I learned some stuff. Specifically: Write what you love. How did J.R.R. Tolkein write about Middle Earth when he had obviously never been there? How does any fantasy, sci-fi, or paranormal fiction writer come up with the things they do--they've never ridden a dragon or piloted a space ship to Mars.
So, in my humble, utterly-unpublished-and-under-qualified opinion, there's really only one rule as far as writing goes. Write something that you would love to read. And, to make it feel true, you have to take it to a place that you know emotionally.
For example, I've spent the past few months desperately trying to write a contemporary YA novel. Why? Because I wanted to write something that I knew. And, somewhere in the back of my mind, this little voice is saying, "People respect contemporary writing. People will take you seriously and say that your book is beautiful and profound. If you write an Urban Fantasy novel, people will ignore you or laugh at you."
That isn't true. And I know better. The thing is, I really couldn't get myself beyond this doubt until just a few days ago, when I started writing something that's kind of fantasy-ish. And it's way more fun than that contemporary ever would've been.
I don't mean to knock true-to-life stories, or even contemporary fiction. I just want you to embrace whatever it is that makes your heart race, and put it down on paper.