The Rule of One for copywriting:

You have one reader. One big idea. One promise. And one offer.

Source: unknown person who is no longer alive, probably in advertising and direct response copywriting in the 1920’s.

“People learn, early in their lives, what is their reason for being,” said the old man, with a certain bitterness. “Maybe that’s why they give up on it so early, too. But that’s the way it is.” - The Alchemist, Paulo Coelho