No less a genius than Albert Einstein recognized the power of creativity. Sure, his left brain mojo was smoking, but the great mathemetician recognized the importance of his right brain, too. He wrote:
“When I examine myself and my methods of thought, I come to the conclusion that the gift of fantasy has meant more to me than my talent for absorbing positive knowledge.”
That’s why there’s no real how-to manual for writing winning copy (or persuasive sales letters or memos or whatever). It’s a function of both halves of your brain… and maybe, like the song says, a little bit of soul.