Probably when I finished my first book. It didn't matter whether it would be published, it didn't matter to me whether it was good or whether people would like it. I had actually created something. Something I enjoyed. And at that point it was good enough for me to move on and take things a step further ... write more with a goal to improve.
When I started writing my very first novel. Of course I wrote tonnes of stories before that point, but none that I would write with the intention to publish, and none that I would ever edit. I just wrote for fun and never looked back. Whether a project was completed or not didn't matter to me. The one I consider my first novel is the one I wrote with the intention to publish and for the first time, actually edited. The quality of the writing mattered. Whether something made sense mattered. Whether it was entertaining to readers mattered. So I guess I felt like a writer when I finally took writing seriously