"For just as we share abundantly in the sufferings of Christ, so also our comfort abounds through Christ." NIV translation
Paul knew about suffering as he had even been stoned and left for dead. He reminds the Corinthian believers that it was Jesus who got him through all of his troubles. Paul is not bragging but he wanted to remind us that it is normal to suffer as a Christian. That is not popular to say today but it is still true.
"If we are distressed, it is for your comfort and salvation; if we are comforted, it is for your comfort, which produces in you patient endurance of the same sufferings we suffer." NIV translation
Paul reminds them that his suffering for the gospel has led to them getting to know Jesus Christ as their Lord and Savior. He also reminds them that his sufferings have shown them what to expect as Christians and how to cope with the persecution of believers. Why do bad things happen to Christians and the more you serve the Lord the more trouble comes your way? It is just as Paul said; our suffering leads people to Jesus and shows them how to cope with a world that is hostile towards God.
"And our hope for you is firm, because we know that just as you share in our sufferings, so also you share in our comfort." NIV translation
Paul expresses his confidence in the Corinthian Christians' ability to stand firm. He could be confident because he knew that they had the same source of strength that he had which is the presence of God through the Holy Spirit.
"We do not want you to be uninformed, brothers and sisters, about the troubles we experienced in the province of Asia. We were under great pressure, far beyond our ability to endure, so that we despaired of life itself. Indeed, we felt we had received the sentence of death. But this happened that we might not rely on ourselves but on God, who raises the dead." NIV translation
Paul is probably talking about his adventure of faith in Lystra where he was taken out and stoned. He reminds the believers that no man has the power to overcome the plan of God. It was not his time to go to heaven so, even after being stoned, he got up again. We must remember that nothing has the power to defeat a man that is following the will of God for their life. He has numbered our days and He is in charge.