Today's feast of the Immaculate Conception means that Mary was conceived free of original sin, and filled with grace from the very first moment of her conception by her mother, St Anne.
Mary was given this grace in view of her future mission to become the Mother of God, when she conceived Jesus virginally by the grace of the Holy Spirit. So the Immaculate Conception is not to be confused with the virgin birth; they're two separate things.
We, on the other hand, are very much subject to sin. Yet this does not put up a barrier between us and Mary, like a concrete highway divider no one can cross. No, the grace given to Mary makes her more human, not less. And she doesn't look down on us. She is a tender Mother who loves all her children, no matter how wayward and caught up in sin they may be.
While we came into the world with the taint of sin, we can go out without it. That's the point of our Christian life. This might be a bit fanciful, but sometimes I like to think about the parable of the Good Samaritan in that light. The man he helped, the one who was beaten up and left for dead, is like a symbol of ourselves in sin. We can become a sorry mess, all spattered with mud and blood and left for dead. We don't hear much about him, but the implication is that after being checked into the inn by the Good Samaritan, the man recovered. He left the inn all cleaned up, and could walk out on his own power.
Mary is like the Good Samaritan. She checks us into the inn of God's grace, where Jesus cleans us up and heals our wounds. He forgives our sins so that we can walk away from sin.
The Immaculate Conception of Mary reminds us that sin doesn't have the final word. Grace does. And grace can triumph over any sin.