The "But I'm an artist!" attitude is a disaster in the making for a writer. That's not to say there isn't an element of artistry in writing. There's also an element of talent. But as in any field, talent and creativity must be wedded to skill and discipline. Architecture can be great art, but without technical know-how and practical-mindedness, even the greatest imagination won't get far building a house you can actually live in.
Writing is a craft. I like the word "craft" because it evokes both skill and artistry. You need imagination to write, but you also need to be ruthless, even brutal in shaping the final product. Writers who are precious about their words end up publishing themselves because no reputable publisher will touch them; the result is poor writing that lacks focus and self-awareness. Family and friends love it, but no one else will buy it or read it.
In publishing, you have to let editors be ruthless with your writing. That doesn't mean blithely accepting everything they say, but it does mean steeling yourself to hear harsh truths. You can't get defensive when an editor says, "This paragraph makes no sense," "You need to revise this entire section" or "This part just doesn't flow." You need to be able to revisit the principles of good writing and work out where you went wrong and how you can put it right.
If you're worth your salt as a writer, you'll be as attentive when no editor is looking over your shoulder. Self-edit without mercy, chopping, rewording and rearranging until you have something that is clear, concise and effective. Resist the urge to hold on to every last word and idea; they're not going anywhere, and there'll be other opportunities.
Don't think I'm not sweating too. I'm very aware of the challenge I'm setting for myself. Discipline is not comfortable, especially for the naturally imaginative, but it's the only way to master a craft -- and writing is a craft.