It’s simply not an adventure worth telling if there aren’t any dragons.

J.R.R. Tolkien (1892-1973) English writer, fabulist, philologist, academic [John Ronald Reuel Tolkien]

(Misattributed)

Variant: "It simply isn’t an adventure worth telling if there aren’t any dragons."

Actually found in Sara Ban Breathnach, Simple Abundance, "February 16: At the End of Our Exploring" (2005). Breathnach quotes an actual Tolkien warning about dragons earlier on the page, apparently leading people to misattribute this phrase of hers to Tolkien.

More discussion: Not a Tolkien quote: It simply isn't an adventure worth telling if there aren't any dragons - thetolkienist.com.