In the [Elvish decision to stay in Middle-earth after the fall of Morgoth] we see a sort of second fall or at least 'error' of the Elves. There was nothing wrong essentially in their lingering against counsel, still sadly with the mortal lands of their old heroic deeds. But they wanted to have their cake without eating it. They wanted the peace and bliss and perfect memory of 'The West', and yet to remain on the ordinary earth where their prestige as the highest people, above wild Elves, dwarves, and Men, was greater than at the bottom of the hierarchy of Valinor. They thus became obsessed with 'fading', the mode in which the changes of time (the law of the world under the sun) was perceived by them. They became sad, and their art (shall we say) antiquarian, and their efforts all really a kind of embalming – even though they also retained the old motive of their kind, the adornment of earth, and the healing of its hurts. We hear of a lingering kingdom, in the extreme North-west more or less in what was left in the old lands of The Silmarillion, under Gilgalad; and of other settlements, such as Imladris (Rivendell) near Elrond; and a great one at Eregion at the Western feet of the Misty Mountains... But many of the Elves listened to Sauron. He was still fair in that early time, and his motives and those of the Elves seemed to go partly together: the healing of the desolate lands. Sauron found their weak point in suggesting that, helping one another, they could make Western Middle-earth as beautiful as Valinor. It was really a veiled attack on the gods, an incitement to try and make a separate independent paradise. Gilgalad repulsed all such overtures, as also did Elrond. But at Eregion great work began – and the Elves came their nearest to falling to 'magic' and machinery. With the aid of Sauron's lore they made Rings of Power ('power' is an ominous and sinister word in all these tales, except as applied to the gods). - J. R. R. Tolkien, Letter 131, ca. late 1951, bold by squre.

The Second Age ends with the Last Alliance (of Elves and Men), and the great siege of Mordor. It ends with the overthrow of Sauron and destruction of the second visible incarnation of evil. But at a cost, and with one disastrous mistake. Gilgalad and Elendil are slain in the act of slaying Sauron. Isildur, Elendil's son, cuts die ring from Sauron's hand, and his power departs, and his spirit flees into the shadows. But the evil begins to work. Isildur claims the Ring as his own, as 'the Weregild of his father', and refuses to cast it into the Fire nearby. He marches away, but is drowned in the Great River, and the Ring is lost, passing out of all knowledge. But it is not unmade, and the Dark Tower built with its aid still stands, empty but not destroyed. So ends the Second Age with the coming of the Númenórean realms and the passing of the last kingship of the High Elves. The Third Age is concerned mainly with the Ring. The Dark Lord is no longer on his throne, but his monsters are not wholly destroyed, and his dreadful servants, slaves of the Ring, endure as shadows among the shadows. Mordor is empty and the Dark Tower void, and a watch is kept upon the borders of the evil land. The Elves still have hidden refuges: at the Grey Havens of their ships, in the House of Elrond, and elsewhere. ... The Ring is lost, for ever it is hoped; and the Three Rings of the Elves, wielded by secret guardians, are operative in preserving the memory of the beauty of old, maintaining enchanted enclaves of peace where Time seems to stand still and decay is restrained, a semblance of the bliss of the True West. - ibid., bold by squre.

"the delight and pride of Aulë is in the deed of making, and in the thing made, and neither in possession nor in his own mastery; wherefore he gives and hoards not, and is free from care, passing ever on to some new work." (JRRT, Sil, "Ainulindale")

"Those who made [the Elvish Rings] did not desire strength or domination or hoarded wealth, but understanding, making, and healing, to preserve all things unstained. These things the Elves of Middle-earth have in some measure gained, though with sorrow. But all that has been wrought by those who wield the Three will turn to their undoing, and their minds and hearts will become revealed to Sauron, if he regains the One. It would be better if the Three had never been." (LotR II.2, italics by squire)