Maglor
I went to a list of phobias and got a random number generator to pick a phobia and here it is: Mnemophobia- Fear of memories.
Enough years of wandering by yourself and trying to forget will do that to you. I think Maglor got to the point where he effectively forgot everything at times, the good and the bad.
"In many cases, mnemophobia doesn't come on suddenly, as it would after a particularly damaging psychological trauma. Sometimes, mnemophobia develops slowly, as the psyche finds more and more reasons to associate negative consequences with the act of having memories. In cases where mnemophobia comes on slowly, psychologists often can't pinpoint a singular reason for the disorder."
Well that just makes it worse. Imagine Maglor, not right after discarding the Silmaril, but after reflecting on his sorrows for long enough gradually beginning to fear his memories and avoid them to protect himself.
After all these years, never talking to anyone save the occasional animal, sleeping rarely and dreamlessly, Maglor had almost forgotten why he was so sorrowful. Until Elros showed up and ruined everything.
"Maglor." He jumped at the sound. Who here knew his name? Forgetting came easily after all this practice; remembering was harder. But he knew who it was even without turning.
"Elros." His voice cracked. He had used it to sing, but not to speak in years. "How did you find me."
"I have my ways. May I sit?"
Maglor moved over on the cliff side he sat on and Elros sat beside him. Now Maglor startled looking at him, seeing the aged man sitting beside him, so different from the elfling he had known.
"Why have you come?"
"Because Elrond possibly never will, and because I am not long for this world."
Maglor was silent, his heart hammering as he feared what Elros would say.
"I know you grieve, Maglor, I will not tell you not to. But Elrond and I both deserved to see you one last time."
"I caused the two of you enough pain." Maglor answered flatly. "I would not impose my company on you any longer. Please do not make me relive any of it."
"You could sail West. You have punished yourself enough, I am sure the Valar would allow you there."
"Perhaps before we stole the Silmarils. After, no." What would he possibly say, to the Valar or his kin, if he were to show up there?
"Why do you not go to Mandos, then?"
"Perhaps I will, eventually. If I am just waiting there or here, I'd just as soon do it here."
"You still do not have to be alone. Elrond would welcome you. He and Galadriel both tried to find you." Maglor looked even more alarmed, so Elros added "Fear not, I did not tell either of them I had found you."
"Elros, after what I did even I do not welcome me."
"That does not mean others won't, Maglor." Elros sounded tired beyond his years, before Maglor remembered that he probably saw years differently as a mortal than he had before.
"What would you have me do?" Maglor asked.
"Waste away for years here, if you must. But one day Elrond will sail West, and then you should find him and go too."
Maglor laughed, his laugh empty of mirth. They both knew that it wouldn't happen.
"I am sorry for all the trouble I caused you and Elrond, please do not try to make me cause any more. If that is all you came for, you should go."
"I will. But not before reminding you that Elrond and I both loved you as the father you were to us. And you deserved it; you still do." Maglor closed his eyes shut and winced. It wasn't what he wanted to hear.
Elros stood to leave, but not before wrapping Maglor in a long embrace, even as Maglor struggled.
"Good-bye, Maglor." Elros said, and was gone.
Farewell. He thought, but he said nothing, calming his breathing and humming a quiet tune of nothingness that spread blankness through his mind again, feeling his pulse still and his tension slip away as his memories faded to blankness again.