For me personally, and I know a ton of people will disagree with me, but I wouldn't call myself a writer unless I was writing a lot. Constantly. Every day. I feel like being a writer is really easy, you just have to stop thinking about writing and actually write. But if you're not writing you're not a writer.

Sometimes I am a writer and sometimes I'm not; it's a fluid state. Right now I'll admit I probably am because I'm writing a couple thousand words a day. But there have been months where I haven't written at all (outside of things like forums) and I would not call myself a writer during those periods of time.