All karma must be paid. Jesus told us this. Those who live by the sword shall die by the sword.
Numbers 14:18 also tells us this. Only the guilty pay for their past crimes -- the sins of the father who is reborn and pays in the 3rd or 4th generation. The lesson of Jacob and Esau also taught us this -- that Esau's past crimes caught up with him even in his mother's womb.
But it seems that payment is not complete unless we are grateful to God for everything that happens to us. This includes medical issues.
If we love God, Jesus, our fellow humans and even our enemies, then our focus of attention is on good. The feelings we have are our asking. And we have only to ask and then we will receive. Too many think one thing, but ask for something entirely different. By their worry, they are creating an environment toward which they can continue to worry. God wants us to be fearless.
And, without faith it is impossible to please God (Heb. 11:6).
So, "bad" things are blessings in disguise.
As immortal children of God, when we take 100% responsibility with love, we can never be a victim. We regain immortality within His loving arms.