I was an English major, too—the kind of person who's supposed to come out of school flinging verbs like throwing stars and building walls of raw grammar. And I was good at being an English major. I read books and I wrote papers and I got good grades on them.
But being an English major is not the same thing as being a writer, much like being a student is not the same thing as being a person. Students must jump hoops in timed competitions to see where they stack up against each other. Their skills are relative and disposable. Real people in the real world must build themselves up so not to starve or fall into a hopeless pit of useless self-loathing. Real people in the real world have real things at stake beyond a letter next to their name.
The thing is, it isn't necessarily hard anymore to learn how to be an English major. Most of my peers did very well in the class. It was almost as if my professors and T.A.s graded on participation and effort alone. Show up to class and look excited for ninety minutes and you get a shiny, polished A. Even the papers, the meat of an English major's labor, were graded simply on the hoops they had to jump—on bare and simple criteria, not as a whole.
The thing about writing is that it is a craft as much as a labor. You can create a written work that argues with plenty of evidence how Hamlet's psychosocial undercurrents disallow the possibility of free will, but unless you do it in an architecturally engaging way, you're just connecting dots. Graders of English papers don't much care how you say what you're saying it. They just care that you're saying it so they can stop reading the bile you dredged up from the pit of your guts at four-thirty this morning. They've got better things to do, so they check that you hit all the notes and they move on to the next jerk's essay.
A writer friend of mine who's also a math major recently bemoaned to me that because he hadn't majored in English, he had never been taught to write. I told him that you don't learn to write by majoring in English. I didn't, at least. You learn to write by writing, and writing diligently—picking apart every new word and finding ways to make it elastic, building up elegant towers of sentences that stop just before they get too big and topple. You read writers you admire and then you write a lot and then when you think you could never write another word you keep writing. You build up that brain-muscle—because unlike your English thesis, writing well is one task you'll never be able to B.S.