Disclaimer: I obviously own nothing.
Gratitude was a lesson hard learned. Especially for those who were prideful creatures, longing for acceptance in a harsh world as something great.
King Thranduil, an elf that clung to his pride, swallowed hard when he looked upon the aftermath of the battle with the orcs, and felt grateful.
His son was alive, as was he, and most of his soldiers would live to see another day. Yet this sort of gratitude was not satisfying.
The Durins lay dead, never to see the glittering jewels and gold in their halls.
Shame intertwined with gratitude was much harder lesson to learn.
This is set sometime after the Battle of the Five Armies, and is canon.