You will recall that imperfect contrition is "Sorrow for sin animated by a supernatural motive that is less than a perfect love of God. Some of the motives for imperfect contrition are the fear of the pains of hell, of losing heaven, of being punished by God in this life for one's sins...[It] is sufficient for remission of sin in the sacrament of penance."1
Remember that perfect contrition of is "sorrow for sin animated by a perfect love of God."
I think that one way to achieve perfect contrition may be to meditate on imperfect contrition.
You know how people (like us parents) say, "you say you're sorry, but really you're just sorry you're going to get punished?" Imagine if we said that to our child and they said "That's true. I am sorry because I'm afraid of punishment." Would you say "Well then, dear child, then I completely forgive you." Or, "Oh, you're sorry because you're afraid you'll miss out on dessert? Well then, you are completely and utterly forgiven. Come. Have the dessert." It's laughable, but this is precisely what imperfect contrition is.
Martin Luther rejected this idea of imperfect contrition. He believed it was hypocritical and actually sinful to be sorry in this way. You can kind of understand his position. *We* would never act this way. God does though. We offer Him the most pathetic reasons for being contrite for our sins--to call it imperfect dramatically understates the reality--and He happily accepts them.
Perhaps then, if we have imperfect contrition, we can think about how unfathomably merciful God is to us. We give Him fear of punishment for our sin and He gives us Himself on the cross as the recipient of that just punishment. We give Him fear of losing heaven, and for *that* He offers heaven in return!
Somewhat paradoxically then, reflecting on our imperfect contrition ought to lead us toward a deeper love of Lord, as we realize He accepts these poor gifts from His children. The more we reflect on how little and sad our contrition is, and how great the reward, the more this contrition can turn outward from self, and more towards the good God who accepts it. In turn, God willing, our imperfect contrition can become the means whereby we finally experience a perfect contrition. Then, we can truly proclaim, "...I detest all my sins... because I offended Thee my God, who art all good and deserving of all my love."