Experiencing chronic migraine as a family has caused us to ask God much about the purpose of suffering in our life. Many times we have sensed him showing us a purpose for which he is using our suffering, or a cause of it. Other times we don't know exactly why, but we remember that suffering on this earth is caused by the presence of sin in general, and we are challenged again to come to the Cross of Jesus... and trust in the GOODness and sovereignty of our Father. This video does a good job of explaining the things we have learned about God and suffering.
David Platt on the Doctrine of Suffering from Desiring God on Vimeo.
What have you learned through suffering?