What is a writer? Is just calling yourself one enough?
Does consistency matter, writing daily/weekly/monthy?
Is publication a requirement? Once published are you forever a writer -- whether you're writing anymore or not?
The gist of my comments follows:
To me, a writer is someone fulfilled by the act of writing. Personally, I don't feel fulfilled if I haven't finished and submitted anything for some time (the exact time varies). Publication isn't required, but most writing is done with an audience in mind, so why not try to publish?
Non-writers might consider someone who wrote one great piece to be a writer; I think writers expect more of themselves, hence the idea that one is not a writer unless one is writing...For example, I've thought about writing a lot, but until I actually write it, I haven't written a lot.
Length doesn't matter (says the poet).
...Each writer has a different idea of success. For me, success is finishing and submitting my work to an editor/publisher other than myself. My idea of success doesn't include my work being accepted because I never know which of my pieces will be accepted. I only know the chances of acceptance are greater if I keep writing and submitting than if I don't. For someone else, success may be writing and publishing books all on one's own. I have nothing against others' ideas of success; I just know they're not for me.