All experiences of suffering in the path of Christian obedience, whether from persecution or sickness or accident, have this in common: They all threaten our faith in the goodness of God and tempt us to leave the path of obedience. Therefore, every triumph of faith and all perseverance in obedience are testimonies to the goodness of God and the preciousness of Christ – whether the enemy is sickness, Satan, sin or sabotage. Therefore, all suffering, of every kind, that we endure in the path of our Christian calling is a suffering 'with Christ' and 'for Christ.' With Him in the sense that the suffering comes to us as we are walking with Him by faith, and in the sense that it is endured in the strength that He supplies through His sympathizing high-priestly ministry (Hebrews 4:15). For Him in the sense that the suffering tests and proves our allegiance to His goodness and power, and in the sense that it reveals His worth as an all-sufficient compensation and prize.
John Piper