Are you funny? Do your friends laugh a lot when you share little anecdotes? If you're funny by nature, you might really struggle to write a tragedy or dramatic novel. If you're not a touchy-feely affectionate person, maybe romance isn't your genre. You should write in a way that's true to your own nature...because this is how you'll do your best writing.
The Voice
You've probably heard about authors who need to find their voice, or the ones who already have. Your voice is really just your natural personality, and the way it appears on the page. Certain writers have their own distinct style, a way of writing that evokes certain feelings.