"Poetry should surprise by a fine excess, and not by singularity; it should strike the reader as a wording of his own highest thoughts, and appear almost a remembrance.  Its touches of beauty should never be half-way, thereby making the reader breathless, instead of content.  The rise, the progress, the setting of imagery should, like the sun, come natural to him"

~ John Keats (1795 - 1821) Letter to John Taylor, Feb. 27. 1818

"If poetry comes not as naturally as leaves to a tree it had better not come at all."

~ Letter to To Benjamin Bailey, March 13, 1818


Source:  THE OXFORD DICTIONARY OF QUOTATIONS

[There are those who would disagree with Keats pronouncement!]