This is from a letter that he wrote to a reader defending his telling of fairy-stories:

\ufffdDear Sir,\ufffd I said\ufffdAlthough now long estranged,
Man is not wholly lost nor wholly changed.
Dis-graced he may be, yet is not de-throned,
and keeps the rags of lordship once he owned:
Man, Sub-creator, the refracted Light
through whom is splintered from a single White
to many hues, and endlessly combined
in living shapes that move from mind to mind.
Though all the crannies of the world we filled
with Elves and Goblins, though we dared to build
Gods and their houses out of dark and light,
and sowed the seed of dragons\ufffd'twas our right
(used or misused). That right has not decayed:
we make still by the law in which we're made.\ufffd

Quoted in [link|http://larsen-family.us/~1066/onfairystories.html|On Fairy-Stories], which itself is a decent explanation of what Tolkien thought of fantasy, and his explanation of why fantasy has been so neglected in English literature.

Ironically he predicted that the Lord of the Rings would always be a failure as a dramatic performance. He was at least somewhat right - to the extent that the movie succeeded it was because the movie makers recognized as Tolkien did what couldn't be done, and consequently left out most of the tapestry that made up Tolkien's world. However it is also clear that movies today can partially transcend the limitations of drama.

But I'll let you read his critique of his life's interest for yourself. I've already read it, and know that communicating what it says to me is beyond my abilities. I can repeat disjointed lessons that I've taken from it, but not the whole picture that it presents on how our imagination and personal stories take internal shape when we least expect it to.

Cheers,
Ben