In Tolkein's Lord of the Rings saga, the War of the Ring ended, some members of the fellowship leave to sail across the seas and find rest in Valinor. Others find peace and success settling back into their old lives with renewed confidence, and some of them champion an era of peace and prosperity for all those around them as well as themselves. Aragorn was one such character. He used his throne and his reign to strike up allegiances, to share in the bounty and the joys of Middle Earth, and to protect the world that they had fought so hard to build. After becoming the king of Gondor, Aragorn set about establishing the Re-united Kingdom, in close companionship with King Eomer of Rohan, and with Merry, Pippin and Samwise in The Shire. He and Arwen guided their peoples for many long years into the Fourth Age, until it was time for their son to take the throne and continue their legacy.
As a member of the Dunedain, Aragorn is blessed with an extraordinarily long life, and his ancient Numenorean blood helps keep him youthful and healthy far longer than normal Men. During the time of the War of the Rings, Aragorn is 87, much to the surprise of the young Eowyn who falls for him. His reign continues for another hundred years or more before he passes it down to Eladrion, and starts the slow decent into old age. And when he reaches 210, Aragorn is finally laid to rest in the halls of his forefathers. But many fans have questioned if this was a personal choice of Aragorn's, and whether he had the ability to choose when to end his life.
There could be two possible reasons for this. The first could be that because Arwen has given up her immortality in order to be with him, Aragorn has a part of that immortality within himself, and therefore has to choose to forsake this when he feels that it is his time to go. This would work in the same way as films such as Stardust (2007), in which Yvaine the fallen star chooses to share her immortality with Tristan, the only remaining heir to the throne of the kingdom of Stormhold. When they have completed their long reign, they choose to light a Babylon candle, and return to Yvaine’s home in the sky as stars, thus essentially ending their lives but still being able to look down on the world below and watch over the ones they love.
This could be the same in Lord of the Rings, where Aragorn chooses to relinquish the immortality that Arwen has shared with him, because he feels that he has fulfilled the things he wanted to achieve in his life. Arwen then retreats into Lothlorien, the woodland of her childhood, and relinquishes her part of the immortality. She is laid to rest in Cerin Amroth, the heart of elvendom on Middle Earth.
Alternatively, perhaps Aragorn was able to choose to end his life due to the ancient gift given to the Numenoreans by Eru Illuvatar, the creator of all things. Because the Numenoreans were such a heroic and valiant race of beings, it was a great fear and concern of theirs that they would grow weak and old and senile, and not be able to find their way back into the light of their creator. They were then awarded the gift of choice, so that they could choose to be reunited with Eru on their own terms, rather than waiting for age to ensnare them. Therefore, if Aragorn had chosen to end his life at 210, it would not have been a euthanasia or a terrible form of suicide, but a peaceful way to lay down and sleep until he has passed into memory and legend through the generations that come after him.
Many Numenoreans began to fear death, or fear a death that wasn’t mighty and honorable — like the death of Boromir, who died for a just cause, protecting his friends. They began to grow jealous of the immortality of the elves, and to rebel against the Valar, who then denied them entry to the Undying Lands. But Aragorn has lived a long and satisfying life, has left the world in a much better state than when he came into it, and is sure of the peace that his son will continue after his death. For him, the choice to be able to rest after all that he has achieved would be a blessing, one that he would welcome after his many long years of ceaselessly caring for those around him. Therefore, it is true that Aragorn did have the power to choose when he died, and did end his days at over 200 years old.