Lamenting our sin

Lamentations is probably one of the least read OT books with its long descriptions of how God's wrath has afflicted Israel.
As you read of the horrors perpetrated against men, women and children (e.g. Lam 2:11-12), you want to think that this is all the responsibility of the Bbylonians, but then you read Lam 2:1ff, and you have to face the fact that, somehow, God stands behind all this - in 2:1-19 we read twenty-six times that the LORD has done this. Then in chapter 3, the author gets personal; it's not now unknown Israelites who suffer, but our author himself who is in agony under the LORD's hand (Lam 3:1-18).
But then there's the most astonishing - shocking - turnaround (Lam 3:19-25).

Now I bet you recognise verses 22f:

The steadfast love of the Lord never ceases;

his mercies never come to an end;

they are new every morning;

great is your faithfulness.

We love to recite that, but as is so often the case with 'nice' OT verses, we've completely forgotten the context - the horrific context - the context of God's unleashed wrath against a faithless, idolatrous, disobedient people. And not just any people, his own covenant people.
But even if we do remember the context, how do we read this as NT, post crucifixion believers? Are we to say, as a young and sincere Christian once said to me, that my suffering (a slipped disk, in my case) was due to a specific sin, and I must confess it in order to be healed? In other words, does God punish our sins and wait for us to repent?
Perhaps the words from the service of the Lord's Supper can help us here. Cranmer (who wrote the original service) was clear about the seriousness of our sin. Having read the commandments to remind the people of their sin, and having read long exhortations and reminders of the seriousness of sin, the minister then leads the congregation in the confession:

ALMIGHTY God, Father of our Lord Jesus Christ, Maker of all things, judge of all men; We acknowledge and bewail our manifold sins and wickedness, Which we, from time to time, most grievously have committed, By thought, word, and deed, Against thy Divine Majesty, Provoking most justly thy wrath and indignation against us. We do earnestly repent, And are heartily sorry for these our misdoings; The remembrance of them is grievous unto us; The burden of them is intolerable. Have mercy upon us, Have mercy upon us, most merciful Father; For thy Son our Lord Jesus Christ's sake, Forgive us all that is past; And grant that we may ever hereafter Serve and please thee In newness of life, To the honour and glory of thy Name; Through Jesus Christ our Lord. Amen.

But then, the minister reads the reassuring words of Scripture:

Hear what comfortable words our Saviour Christ saith unto all that truly turn to him.

COME unto me all that travail and are heavy laden, and I will refresh you. Matthew 11.28
So God loved the world, that he gave his only-begotten Son, to the end that all that believe in him should not perish, but have everlasting life. John 3.16
Hear also what Saint Paul saith :
This is a true saying, and worthy of all men to be received, That Christ Jesus came into the world to save sinners. 1Timothy 1.15
Heare also what Saint John saith:
If any man sin, we have an Advocate with the Father, Jesus Christ the righteous; and he is the propitiation for our sins. 1 John 2.1

And then, in the prayer of thanksgiving, he reminds us again of the completeness of our salvation:

ALMIGHTY God, our heavenly Father, who of thy tender mercy didst give thine only Son Jesus Christ to suffer death upon the Cross for our redemption; who made there (by his one oblation of himself once offered) a full, perfect, and sufficient sacrifice, oblation, and satisfaction, for the sins of the whole world...

In all of this Cranmer was reflecting the clear message of the promises of the OT (e.g. Jer 31:34) and the NT that the punishment for sin fell on Christ so that it does not fall on us. So, returning to the question of the cause of our suffering, we see that it cannot be due to God's punishment for our sin - that was fully dealt with at the cross by Jesus.
However, there is another strand in the NT, and that is the Lord's discipline. The classic text for this is  Hebrews 12:4-11, but in Romans 5:1-5 we see that Paul first insists that we have peace with God before then explaining the cause of our suffering - to produce endurance, character and hope.

So our experience of God is different from that of the OT people of God. They experienced God's wrath for themselves, in the hope that they would return to God and receive his love and mercy. And as we read of the horror of being under the wrath of God, we should remember two things. First, it's a picture of hell, and second, it's a picture of what Jesus suffered for us.
And this should spur us on to praise and thank the Lord Jesus for his sufferings on our behalf, offering our whole lives to him in worship and adoration as a 'living sacrifice' (Rom 12:1). And it should remind us that our loving Father disciplines us for our good and for his glory, that we might be more holy and better reflect the image of Christ.