Karl Anders Ericsson is a Professor of Psychology at Florida State University: he has a world-wide reputation in the study of expertise, practice and success.
In the early 1990s Ericsson discovered a pattern to the careers of the violinists and pianists who studied at the Music Academy of West Berlin: while they were all exceptionally talented, the students who experienced international success all practiced around three times longer each day than their less successful classmates (you can download a PDF of Professor Ericsson’s paper here).
When he investigated further, he discovered that this dedication to practice applied to just about everyone: including chess players, scientists, artists and writers.
Ericsson concluded that all that was necessary to become an expert in any subject was to put in four or more hours of regular practice over a period of at least ten years. He found no evidence that talent was required.
If you want to write really well, then you’re just going to have to keep at it. There are no shortcuts. Just get your words down on the page. And keep at it. For as long as it takes.