What You Need to Make It as a Professional Writer: My Two Cents
1) A ridiculous drive to do nothing else, to the frenzied point where you're dreaming constantly of words and stories and sentences.
2) An insatiable reader of great work. You have to know what great work looks like before you can create it. All great writers had many influences.
3) Conviction. Nobody can convince you that you're a great writer unless you feel it inside. And unless you have that confidence, it will be hard, if not impossible for you to keep on keeping on.
4) Great leaping ability. Over rejection and failure. Over harsh criticism and bad writing days. And especially over negativity and people telling you to try something else.
5) Talent. As much as you may have all of the above, unless you have the talent to put words together clearly, succinctly, interestingly, you probably won't attain anything but a minor status in the industry, at best. It's a sad fact, though there are certainly many exceptions to this rule that we can all point to. I have no idea what makes people talented and I'm not sure that you can teach it, but I think I know when I see it and read it. It's a subjective thing, of course, but I know it when the words jump off the page at me.