Jon and John,
You have raised some good points about contrition. Saint Thomas Aquinas teaches in the Summa On Grace that the grace of God is required for man to be contrite for his sins and desire forgiveness. In other words, you could say that man needs God’s grace in order to even desire God’s grace!
The Church teaches that there are two forms of contrition. Imperfect contrition is when a sinner confesses their sins and repents because they fear hell. Perfect contrition results from pure love of God. The sinner is repulsed by their sins simply because they hate sin and seek holiness. Love is their only motivation for turning from sin.
Imperfect contrition is sufficient for salvation but it will not bring the perfection in Jesus Christ that the Father desires for each of us.
One could say that purgatory is where we finally learn perfect contrition, if we have not already. If the believer enters into purgation, hell is no longer a possibility for them. Therefore, imperfect contrition does not exist in purgatory.
Perhaps this will help explain the mystery of purgatory to us. If we are to develop perfect contrition through our purgation then it must involve the outpouring of love. We are brought into unison with the Sacred Heart of Jesus. This would also explain the suffering of purgatory, since love and pain are connected. Therein lies the contrast of purgation. It is at once an experience of joy and sorrow, love and pain, just as this very life is.