Why do bad things happen to good people?

or

The Problem of Suffering

or

The Problem of Pain

This problem is actually as subset of the Problem of Evil, because suffering is a natural evil (as opposed to a supernatural evil). This issue is one that is very difficult for many people and about which many have questions and are seeking a sufficient answer. And as usual Catholicism has the Answer.

The great Saint Thomas Aquinas deals with the problem of evil and suffering, as well as the particular issue of the suffering of the just in his commentary on the book of Job:

The Problem of Evil
The First Lesson: God is Almighty
The Second Lesson: God is Infinitely Wise
The Third Lesson: Job Cannot Struggle against God
The Fourth Lesson: The Cruel Lot of the Just and the Wicked

The Special Problem of the Suffering of the Just
The First Lesson: Job Returns to Himself: The Creator does not deny His Creature
The Second Lesson: Is Job Blameworthy?
The Third Lesson: Job Desires a Respite

This question has also been most ably answered in the wonderful little book: Why Must I Suffer? A Book of Light and Consolation, by Rev. F. J. Remler, C.M. In his work Father Remler breaks down the reasons for suffering in this life into fifteen different categories, which are as follows:

-Sharing the Consequences of Original Sin

-Expiation of Public and National Sins

-Natural Results of Indiscretions

-Natural Results of Sins Against the Ten Commandments

-Temporal Punishment of Your Sins

-A Substitute for Purgatory

­­-The Body’s Share in Making Atonement

-Your Need of Conversion

-Your Need of Perfect Conversion

-Forestalling the Danger of Eternal Perdition

-Making Atonement for the Sins of Others

-Promoting the Welfare of the Church

-Procuring the Conversion of Sinners

-Acquiring Conformity with Jesus Christ

-Predestination to an Exalted Degree of Glory in Heaven