Even if Satan, on his divine leash, has a hand in our suffering and death, he is not ultimate. He cannot hurt us without God’s permission and limitation (Job 1:12; Luke 22:31; 2 Cor. 12:7). And in the end, it is right for us to say to Satan what Joseph said to his brothers who had sold him into slavery: “As for you, you meant evil against me, but God meant it for good” (Gen. 50:2
Be careful not to water this down. It does not say, “God used it for good” or “God turned it for good.” It says, “God meant it for good.” They had an evil purpose. God had a good purpose. God didn’t start cleaning up halfway through this sinful affair. He had a purpose, a meaning, from the beginning. From the start, he meant it for good. 
This is the key to comfort when the evil of men and the evil of Satan compound our suffering. In Christ, we have every right to say to Satan (or to evil men), “You meant it for evil. But God meant it for good.” 
Neither Satan nor sickness nor sinful man is sovereign. Only God is. And he is good—and wise and sovereign.

*John Piper