“Frodo undertook his quest out of love–to save the world he knew from disaster a

“Frodo undertook his quest out of love–to save the world he knew from disaster at his own expense, if he could; and also in complete humility, acknowledging that he was wholly inadequate to the task. His real contract was only to do what he could, to try to find a way, and to go as far on the road as his strength of mind and body allowed. He did that. I do not myself see that the breaking of his mind and will under demonic pressure after torment was any more a moral failure than the breaking of his body would have been–say by being strangled by Gollum, or crushed by a falling rock.

That appears to have been the judgement of Gandalf and Aragorn and of all who learned the full story of his journey. Certainly nothing would be concealed by Frodo! But what Frodo himself felt about the events is quite another matter.

He appears at first to have had no sense of guilt; he was restored to sanity and peace. But then he thought that he had given his life in sacrifice: he expected to die very soon. But he did not, and one can observe the disquiet growing in him. Arwen was the first to observe the signs, and gave him her jewel for comfort, and thought of a way of healing him. Slowly he fades ‘out of the picture’, saying and doing less and less. I think it is clear on reflection to an attentive reader that when his dark times came upon him and he was conscious of being 'wounded by knife sting and tooth and a long burden’ it was not only nightmare memories of past horrors that afflicted him, but also unreasoning self-reproach: he saw himself and all that he [had] done as a broken failure. 'Though I may come to the Shire, it will not seem the same, for I shall not be the same.’ That was actually a temptation out of the Dark, a last flicker of pride: desire to have returned as a 'hero’, not content with being a mere instrument of good. And it was mixed with another temptation, blacker and yet (in a sense) more merited, for however that may be explained, he had not in fact cast away the Ring by a voluntary act: he was tempted to regret its destruction, and still to desire it. 'It is gone for ever, and now all is dark and empty’, he said as he wakened from his sickness in 1420.

'Alas! there are some wounds that cannot be wholly cured,’ said Gandalf–not in Middle-earth. Frodo was sent or allowed to pass over the Sea to heal him–if that could be done, before he died. He would have eventually to 'pass away’: no mortal could, or can, abide for ever on earth, or within Time. So he went to both a purgatory and to a reward, for a while: a period of reflection and peace and a gaining of a truer understanding of his position in littleness and in greatness, spent still in Time amid the natural beauty of 'Arda Unmarred’, the Earth unspoiled by evil.”

—J.R.R. Tolkien, The Letters of J.R.R. Tolkien, “246” (Part of his reply to a reader’s comments on Frodo’s failure to surrender the Ring in the Cracks of Doom)