Philosophers talk about the nature of experience and how important this is in "knowing" stuff, which is called epistemology, or the theory of knowledge. Empiricists believe that we ultimately learn through experience, in opposition to Rationalists who believe in the concept of innate knowledge, or "knowing" stuff from birth, like we've been pre-programmed. In other words, this is a nature/nurture debate, with Rationalists going for nature and Empiricists going for nurture. Plato and Descartes were famous Rationalists, John Stuart Mill and David Hume famous Empiricists.
Me? I'm 60/40 in Rationalism's favour. Though I believe absolutely in Empiricism and how experience is important in defining and refining one's skills, I do happen to believe that one has to have a pre-disposition towards that skill in the first place - hence the thought in me that certain things have to be "innate". Hell, maybe that belief is innate. I'm not sure, since I don't even know where everything in me came from. Why am I a scriptwriter? No one else in my family is like me. Not one. Though there are many creative people, my mother is a fantastic pianist for example and won many music competitions and awards in her youth - yet none of them write. All are creative with reference to performance - something I have zero interest in: acting? singing? playing in a band? No thanks - and in any case, all of these interests are secondary to my siblings, bar one. One is a doctor, another a nurse. One is still "considering her options" though she thinks she might want to be a property developer. Only my last sister is even remotely like me in that she wants to be a singer and actor, which is of course nothing like a writer but considerably closer than the medical profession.
So, Rationally, I believe that BEING a writer is innate. It's not a job, where you clock in and clock out; it's beyond that kind of control. You ARE a writer, it's a state of being. But writing is an Empiricist pursuit as well. Take the redrafting process for example. Who writes a perfect draft, first time? No one, that's who. I like to think I'm a good writer, but always, always, there are opportunities missed, mistakes made, structure fucked up, characters unneccessary, arena forgotten and so on in every first draft I've ever written. Just yesterday I posted about my god-awful first script that had many drafts but is STILL THE WORST SCRIPT IN THE WORLD and should never see the light of day. I don't write crap like that any more. Even a mediocre writer has to move on, become more sophisticated, write more coherently.
So keep Rationalism and Empiricism in mind, especially when you've been rejected or you doubt yourself. You wouldn't want to be a writer if it wasn't IN you, somewhere, an organic part of you. And experience always makes us better. Practice makes perfect might be a cliche, but cliches are cliches because they carry a grain of truth.
You ARE a writer. So write. And learn.