Charisma?

[Raynor]

Then again, the quote implies, to me, that the gifts and grace come from "outside" : "'by ordained individuals inspired and guided by an Emissary to ends beyond their individual education and enlargement'.
There are many features of their race which are critical to the achievement of the quest:

Originally Posted by Letter #109

I think that there is no horror conceivable that such creatures cannot surmount, by grace (here appearing in mythological forms) combined with a refusal of their nature and reason at the last pinch to compromise or submit.

Originally Posted by Letter #131

They are entirely without non-human powers ...and abnormally, for humans, free from ambition or greed of wealth. They are made small (little more than half human stature, but dwindling as the years pass) partly to exhibit the pettiness of man, plain unimaginative parochial man – though not with either the smallness or the savageness of Swift, and mostly to show up, in creatures of very small physical power, the amazing and unexpected heroism of ordinary men 'at a pinch'.

There is also a quote (in the letters I believe) where it is said that Frodo received just enough grace to bring the quest to the end. All in all, I would say we have the good and normal side of humans rising to face great challenges.