It is true a person's struggles in life does not end when he becomes a Christian.
But we have a very important difference from non-believers.
The difference can be found in these verses:
"And we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose." (Romans 8:28)
"For I am convinced that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers, nor height, nor depth, nor any other created thing, will be able to separate us from the love of God, which is in Christ Jesus our Lord." (Romans 8:38-39)
1. When we suffer because of our sins, we are discipline by the Lord.
When the Corinthian church did not honor Jesus in taking communion (but they treated it like common food), some of them got sick and some died.
"So then, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord. Everyone ought to examine themselves before they eat of the bread and drink from the cup. For those who eat and drink without discerning the body of Christ eat and drink judgment on themselves. That is why many among you are weak and sick, and a number of you have fallen asleep. But if we were more discerning with regard to ourselves, we would not come under such judgment. Nevertheless, when we are judged in this way by the Lord, we are being disciplined so that we will not be finally condemned with the world." (1 Corinthians 11:27-32)
So God disciplines us to correct us in order for us to not be judged and condemned along with the world.
If we repent, we will be restored. But sometimes the consequences of sin can still be there.
"Do not be deceived, God is not mocked; for whatever a man sows, this he will also reap." (Galatians 6:7)
"My son, do not regard lightly the discipline of the Lord,
Nor faint when you are reproved by Him;
For those whom the Lord loves He disciplines,
And He scourges every son whom He receives." (Hebrews 12:5-6)
So we are disciplined by God when we do wrong in order to correct us.
2. We could suffer because of persecution.
Many Christians suffer worldwide because of persecution by others.
However, when we suffer because of God's word, we are blessed.
"Blessed are you when men hate you, and ostracize you, and insult you, and scorn your name as evil, for the sake of the Son of Man. Be glad in that day and leap for joy, for behold, your reward is great in heaven. For in the same way their fathers used to treat the prophets." (Luke 6:22-23)
The word of God spreads even though Christians are persecuted, because non-believers see that we truly believe and we honor God despite danger to ourselves.
In these sufferings, non-believers could become believers and we are saving lives even if we are persecuted. Moreover, there is a great reward in the future for us if we suffer for the gospel.
3. We could suffer from want.
God sometimes allows us to experience hunger or other types of need in order to direct us to depend on Him.
God led Israel through the wilderness and trained them to depend on Him:
"He humbled you and let you be hungry, and fed you with manna which you did not know, nor did your fathers know, that He might make you understand that man does not live by bread alone, but man lives by everything that proceeds out of the mouth of the Lord.” (Deuteronomy 8:3)
So from our problems, God always teaches us to trust Him more.
"Trust in the Lord with all your heart
And do not lean on your own understanding.
In all your ways acknowledge Him,
And He will make your paths straight." (Proverbs 3:5-6)
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"For as the heavens are higher than the earth,
So are My ways higher than your ways
And My thoughts than your thoughts." (Isaiah 55:9)
God's thoughts and ways are noble. Even in our world, we consider people noble who suffer for others. Job suffered in a noble way. He did not know it at the time, but God used his suffering to teach billions of people even today (through the Bible) how to trust God and how to be noble.
Human thoughts are often shortsighted. We just think: "Oh this is painful. Why do You allow it?". But God uses suffering to help us grow and to help others.
We need to remember that God does not want to grieve us, but sometimes pain is necessary so that lives can be saved.
“Though He brings grief, He will show compassion,
so great is His unfailing love.
For He does not willingly bring affliction
or grief to anyone.” (Lamentations 3:32-33)
In the future kingdom, there will be no more pain:
"He will wipe away every tear from their eyes; and there will no longer be any death; there will no longer be any mourning, or crying, or pain; the first things have passed away." (Revelation 21:4)
Jesus said, "These things I have spoken to you, so that in Me you may have peace. In the world you have tribulation, but take courage; I have overcome the world." (John 16:33)