Sophocles addressed this issue in the Exodos of his play, Oedepus Rex. I know that it is very cliche to say that the purpose of suffering is "so that we learn a lesson", but I am not trying to say that that is the purpose of suffering. Like Rob said in class (about the Matrix), I think that Sophocles was attempting to say that even a life of truth (no matter the level of disgrace you have aquired) is much more worth living than a "successful" life of ignorance. We all mess up and it is best to confront them. Perhaps God allows suffering to "test" our ability to face those issues.
Just a thought.