I only discovered I was a writer comparatively recently, though I have been writing all my life, just not exactly knowing it. I thought I was a dancer, then an academic, then a political activist; along the way, a mum (and wif). I still am all those other things, but not, I think, as much as I am, at heart, a writer.
If I had read this definition of a writer in my youth, I would have known much sooner that I was a writer and saved myself a lot of time and frustration, methinks. I might even be published by now. But it still helps to know, better late than never, the peculiar, potentially potent contradiction that is a writer.