Lamentations 5:15–16 (ESV) … “The joy of our hearts has ceased; our dancing has been turned to mourning. The crown has fallen from our head; woe to us, for we have sinned!”
By these words, the Prophet shows the dreadful desolation that appeared in the city after the people had gone into exile. And among the Chaldeans, and in Assyria, they had not their own judges nor any form of government, for they were dispersed and scattered, and that designedly, that they might not unite together anymore; for it was the purpose of the Chaldeans to obliterate by degrees the very name of the people; and hence they were not there formed into a community.
The prophet pursues the same subject, but he seems more clearly to explain what he had briefly stated in the preceding verse, when he says that all joy of the heart had ceased, and that all the dances were turned into mourning. We know that life is more bitter than death when people are in constant mourning; and truly where there is no hilarity, that state of life is worse than death. And this is what the Prophet now means by saying that all joy had ceased, and that all dances were converted into mourning.
By the crown of the head, the prophet no doubt understands all those ornaments by which that people had been adorned. They had a kingdom and a priesthood, which were like two luminaries or two precious jewels; they had also other things by which the Lord had adorned them. As, then, they were endued with such excellent things, they are said to have borne a crown on their head. But a crown was not only taken for a diadem,—it was also a symbol of joy and of honour; for not only kings then wore crowns, but men were crowned at weddings and feasts, at games also, and theatres. The Prophet, in a word, complains, that though many ornaments did belong to the people, yet now they were stripped of them all: The crown, he says, has fallen from our head.
The reason? The prophet exclaims, Woe to us now, for we have sinned! Here he sets forth an extreme misery, and at the same time shews that all hope of restoration was taken away. He, however, mentions the cause, because they had done wickedly. By saying this he did not intend to exasperate their sorrow, so that they who were thus afflicted might murmur against God; but, on the contrary, his object was to humble the afflicted, so that they might perceive that they were justly punished. It is the same as though he had summoned them as guilty before the tribunal of God and pronounced in one word that they justly suffered or sustained so grievous a punishment; for a just God is an avenger of wickedness.
Jeremiah knew that God could restore Jerusalem, but he wondered if he would. His prayer seems doubtful as well as hopeful, raising the unwelcome prospect that Jerusalem is beyond redemption. Has God utterly rejected his people? Is he angry beyond measure? The possibility of being beyond redemption is so alarming that many Jews refuse to end their reading of Lamentations with the book’s final verse. To this day, whenever the book is read, it is the custom in many synagogues to repeat verse 21 after verse 22.
That is not how Lamentations was written, however. The book ends the way God intended it to end, with the kind of unresolved anguish we have come to expect from the Weeping Prophet. Yet Lamentations was never intended to have the last word. The questions it raises were ones Jeremiah could not fully answer.
There are many times when Christians find themselves asking the same kinds of questions: Has God rejected me? Can I still be saved? Is there any hope? Will my sufferings ever come to an end? In this troubled world, similar questions often need to be asked about the sufferings of others: Why does God allow persecution and oppression? What purpose does he hope to accomplish through warfare and famine?
Unlike Jeremiah, we can do more than ask such questions. We can trust the answer God has provided through the atoning death of Jesus Christ, who makes this promise: “Blessed are those who mourn, for they will be comforted” (Matthew 5:4).
 Calvin, J., & Owen, J. (2010). Commentaries on the Prophet Jeremiah and the Lamentations (Vol. 5, pp. 506–508). Bellingham, WA: Logos Bible Software.