H L Mencken, whom I respect in the same way that a woodcutter respects the tallest eucalypt in the land, once said that "injustice is relatively easy to bear; what stings is justice." And this is very true. I don't mean in the physical sense. A year in jail is not any shorter if you are innocent or longer if you are guilty. A slap does not hurt more if you really made that offensive joke, or less if some other person made the joke but slipped off before the target turned around.
What I am talking about is the ability to endure the suffering: to fix your attention on something beyond it. This is straightforward (though certainly not easy) in the case of injustice. The person suffering injustice, if they know that it is unjust, can see that it should not affect their view of themselves. The authority which dispenses unjust suffering has proven itself no authority at all and its opinion of you can be safely ignored. Almost all suffering is considered by Australian society to be unjust and therefore uninformative - it shows you nothing about the world or yourself.
If you take this point of view then you learn very little from looking at the world. Consider what is humorously called the justice system. Even the energy of a great many dedicated people can do no more than make this system less unjust than the usual chaos of the world. Any decision of a court will contain injustice because it will not be perfectly just. In the case of murder, what would be perfectly just would be to restore the dead to life, perhaps by using some portion of the killer's life force. This is quite impossible.
Instead the usual decision is for the killer to be deprived not of some of their time alive, or some of their capacity to enjoy life, but of their ability to dwell with society while living. How curious. If you want someone to realise that killing is wrong, depriving them of liberty and joy is an odd way to go about it. Many people have preferred death to captivity, and a murderer sent to prison might easily decide that they did their victim a favour in booting them off such a constrained and twisted mortal coil. I am not saying that I know a better decision for the court to make, or that there is one (though I hope there is). I am saying that the manifest injustice of the world should cause a thirst for true justice. But because this injustice is seen as uninformative it is not really processed by society or by the individual.
And because it is not processed by the individual, it is more difficult to endure. It is more difficult to fix your eyes on something beyond the present suffering when there is no reason for the suffering to ever end, because there was no reason for it to begin. Unjust suffering is a trumpet played (badly) at random in the night: you do not know why it began, and you do not know when it will end, so you do not know whether you should simply plug your ears for a few moments or find and admonish the trumpeter.
A Christian, if they are aware of their own sin, has no such trouble. A Christian knows that they are a sinner and that they deserve suffering - an eternity of suffering. I am not saying that there is a causal connection between an individual's sin in this world and their suffering. It is transparently obvious that that is not a general principle. But a Christian knows that sin in general is what caused and continues to cause suffering in general, and that the one cannot be abolished unless the other is as well.
And since a Christian knows that through faith in Jesus, the perfect sacrifice, their sin has been taken away, they can fix their eyes on the day when Jesus will return and abolish further sin and further suffering. Being a Christian does not shield you from suffering. But it gives you the knowledge that suffering in this world is justice, nor injustice; and being justice, it is purposeful; and being purposeful, it will end when its usefulness is at an end. When Jesus returns the usefulness of suffering will come to an end. I can fix my eyes on that while I suffer.