A story adapted from Art and Fear, by David Boyles and Ted Orland, goes like this: A ceramics teacher announced on the first day of class that he was dividing everyone into two groups. One group would be graded solely on the quantity of the work produced, and the other group would be graded solely on the quality of their work. To determine their grades, the teacher would bring in a scale on the last day of class and weigh the work of the "quantity" group; the students in the "quality" group would need to produce only one pot--a "perfect" one--to achieve an A.
Can you guess what happened? The works of the highest quality all came from the group being graded for quantity! While the quantity group was busy churning out piles of work, and learning from their mistakes, the quality group had sat theorizing about perfection, and in the end, had little to show for their efforts.
Likewise, your writing success will come from lots of writing production. Make it your goal to complete more and more pieces of work, and watch the quality of your writing take off.