The final composition is only the end result, and how you get there is just as important as where you end up. Good writers are good, not because they sit down and write effortlessly, turning out beautiful sentences without sweat. They are good because they believe that eventually, after lots of work and time and discarded drafts, they will come up with something worth a reader's attention. Writing is discovery. And the more you write and re-write, the clearer and more interesting your thinking becomes.
Writing is social.
You may feel that you have to be alone to write, and this may be physically true. Writing is not complete until it has reached, physically and intellectually, the audience for whom it was intended. Your enrollment in this course makes you an important contributing member of a supportive, committed writing community. Writing is self-taught. You learn to write by doing it, not by listening to somebody tell you about it.