Grit is just as important as talent. A thick skin is necessary for the rejections, non-responses, bad reviews, and the self-doubt. In graduate school, a successful alum once said to all of us, "the only difference between those of you who will make it as writers and those who won't is who among you is still writing in ten years." At the time I thought, ten years?! But now I think that was the most accurate advice/prediction anyone could have made. Be willing to gut it out for the long haul.