After spending a few Cantos in the ledge of pride, Dante has one of the marks on his forehead taken away, which then dims the rest of them. Remember the marks are the reminder of the seven deadly sins. Pride being the first and the one that leads to all the rest.
Sin, all sin weighs the soul down. Even if a person doesn’t believe in sin or that some vices are no big deal, they weigh us down nonetheless. Like in the ledge of pride, sin is a rock upon our shoulders pressing us down. Reminding us that we are but human, weak, made from the earth. We must be humble, because we really are not that great. In our own power, we are ruthless, unkind, rude, treacherous, terrible, murderous, lustful, you name it. And of course, because we are made in the image of God we are kind, caring, helpful, etc. But our image is marred, muddied, cracked, however you want to look at it. We are weighed down by our own crap that we know is within us, yet we deny as often as possible, or justify our actions.
But owning our own garbage, our own vices and our own virtues is what a mature person does. Knowing who we are, what we are capable of: good and evil.
As we move on, it is wise to move upward. Move with God’s will. Only Christ expiates our sins that weigh us down. Most of the time, the weight of one’s sins is the severe mercy that brings us to our knees–allowing us to only cry out for God’s help and mercy and love and grace. As these weights are taken from our shoulders, as the marks on our foreheads are erased, we become lighter. Able to walk upright. Becoming more like the One who has forgiven us, who makes us like Himself. That we are no longer men (or women) but Christ-like, god-like, perfected in His image. Remade as though before the fall … the top of Mount Purgatory the Garden of Eden that allows us to enter Paradise through the fire of Love.