He is the God who raises the dead (2 Corinthians 1:9). When Paul and his friends suffered so much that they despaired even of life, they took comfort in knowing that God raises the dead. It would matter not if they lost their lives, for God would raise them to life again. This comfort produced patient endurance in their suffering.
He is the God who delivers (2 Corinthians 1:10). Despite feeling the sentence of death in their hearts, God delivered Paul and his friends from their peril. They were granted life to keep working, to keep preaching, to keep suffering and to keep being comforted. They took comfort in knowing that God is the God who delivers. This also produced patient endurance in suffering.
It is knowing this that Paul can say so confidently, "to live is Christ and to die is gain" (Philippians 1:21). It was trusting in the same God that Shadrach, Meshach and Abednego could say,
If we are thrown into the blazing furnace, the God we serve is able to save us from it, and he will rescue us from your hand, O King. But even if he does not, we want you to know, O king, that we will not serve your gods or worship the image of gold you have set up." (Daniel 3:17-18)
Sometimes God will deliver us from death; like he delivered Daniel from the lions, Peter from prison and Paul from the ambush. Sometimes he will deliver us through death into glorious life; like Stephen, like James the brother of John, and like our Lord himself. Always working through everything for our good and for His glory. This is our comfort.