Suffering exists in the world because of sin.
In the beginning, there was no sin. God created our first parents, Adam and Eve, and gave them sanctifying grace. This grace made them holy, and there was no sin. Because there was no sin, everyone enjoyed peace. And because there was peace, there was no suffering and no death.
How sin came to be
In the garden of Eden, where our first parents lived, God gave them a job: to care for the garden. In the garden, there was a tree called the Tree of the Knowledge of Good and Evil and God warned them not to eat the fruit of that tree, because if they did, they would die.
The devil tempted Adam and Eve and they disobeyed God and ate the fruit of the tree.
Disobeying God is sin, and that is how sin came into the world.
How sin caused suffering in the beginning
Because they sinned, Adam and Eve lost sanctifying grace and no longer had the holiness they first enjoyed. And because they sinned, all the peace they enjoyed was gone as well. And because peace was gone, suffering came into the world.
Before they sinned, Adam was friends with God. After they sinned, Adam hid from God, and instead of asking for forgiveness for breaking the law, he blamed his wife. So, there was no suffering between God and mankind.
Before they sinned, Adam protected and loved Eve, and Eve could have children without pain. After they sinned, Adam blamed his wife instead of asking God for forgiveness and Eve became ruled by Adam. So, there was suffering within mankind.
Before they sinned, the land was easy to work with and Adam did not have to work hard to get food. But after they sinned, the land turned against him and it became hard to work with and it no longer became easy to get food. So, there was suffering between mankind and nature.
Before they sinned, they had great knowledge, had control over all their desires, they did not experience terrible pain, and their bodies would have lived forever. After they sinned, their knowledge weakened, their control over their desires weakened, Eve could only have children with intense pain, and their bodies would inevitably fail and decay to dust. So, there was suffering within each person.
Before they sinned, they could have taught their children holiness. After they sinned, by eating the fruit of the Tree of the Knowledge of Good and Evil, they came to know evil, and they taught their children, by accident, good and evil. Thereafter, some of their children were good and some were evil. For example, their first son, Cain, was evil and their second son, Abel, was good, and Cain killed Abel out of jealousy.
How sin causes suffering today
Today, because we are not born with sanctifying grace, our friendship with God has to be worked on over time. Until it is perfected, we will make mistakes that will lead to our own suffering and the suffering of other people.
For example, instead of asking God for forgiveness for our mistakes, we might just blame other people. This causes to hate one another.
Instead of forgiving other people for their mistakes, we might just take revenge on them. This causes us to perpetuate violence against each other.
Instead of us treating each other as equals, we might just try to dominate each other. This causes social classes, inequality, masters and slaves, racism, ageism, sexism and poverty.
Instead of depending on the land to naturally feed us, we have to cultivate the land through various seasons, sometimes under intense heat or terrible cold, store up food in case of famines or shortages, and learn to deal with decaying food.
Instead of trusting that nature would care for us, we have to be wary of dangerous animals such as lions and bears; dangerous insects such as mosquitoes and hornets; dangerous weather events such as tornadoes and hurricanes; dangerous geological events such as landslides and earthquakes; and dangerous diseases such as the plague and the flu.
Instead of always doing what God wants us to do, our natural first reaction is to do what we want to do, which leads us to thinking evil thoughts, saying harmful things, doing evil actions, writing ungodly books, watching ungodly movies, taking dangerous drugs and eating unhealthy food in unhealthy portions. In the end, we end up harming ourselves and harming others, and watching the ones we love die, which all leads to more suffering.
And worst of all, instead of teaching our children holiness, when we live according to our own desires and not God’s, we teach them that it is okay to do the wrong things, which leads our children to doing evil and passing on those lessons to their children.
Our Lord said, “Whoever causes one of these little ones who believe in me to sin, it would be better for him if a great millstone were hung round his neck and he were thrown into the sea.” – Mark 9:42
How suffering leads to holiness
Life would be a terrible tragedy if we were born with no end in sight except suffering. Sadly, this is what many people thought in the past and what many think today. That is why many people continue to sin and create more suffering for themselves and others, because they think that nothing will change.
But, when Our Lord Jesus Christ came to save us, He showed us that the end of our life is not suffering, but eternal joy.
To reach that eternal joy, we must perfectly love Christ. And how do we become perfect? Through suffering.
Accept whatever is brought upon you, and in changes that humble you be patient. For gold is tested in the fire, and acceptable men in the furnace of humiliation. – Sirach 2:4-5
Then Jesus said to his disciples: If any man will come after me, let him deny himself, and take up his cross, and follow me. For he that will save his life, shall lose it: and he that shall lose his life for my sake, shall find it. – Matthew 16:24-25
By enduring suffering, we can do good both when it is easy and when it is hard and thereby make it a habit. By enduring suffering, we can love Christ when it is popular and when it is not and thereby make it a way of life. By enduring suffering, we can imitate Christ and join our pains to His cross and thereby extend His mercy to all those in our world.
We were perfect and holy when we were first created. By choosing to sin, we became imperfect and created suffering. Now, by enduring suffering with the help of the Holy Spirit, we can again become perfect and holy.
Remember, humans created suffering, not God. But, God turns suffering into our opportunity to become holy.
We know that in everything God works for good with those who love him, who are called according to his purpose. – Romans 8:28