In Jesus Christ we have been chosen and destined in accord with the purpose of God for creation. The traditional and popular understanding of the feast of the Immaculate Conception of the BVM is that because Mary was chosen to be the mother of God’s begotten son, God spared her from the stain of original sin. It is a recognition that sets Mary apart from the rest of humanity, so to speak, for so spared, she did not inherit that sin which is common to descendants of Adam and Eve. Does this mean that today’s feast is only celebrated nostalgically by the Church? If not, what does the feast mean for us who celebrate it today, we who without any doubt have inherited the sin of Adam and Eve?
While today’s feast certainly puts Mary on a pedestal, it does so for our benefit. Mary is not elevated in denigration of the rest of humanity. Rather, she is put forth on a pedestal as role model and as a sign of hope for the rest of humanity, that humanity can still attain the purpose and will of the Creator. Because of Mary being spared the stain of original sin, Mary was able to live to the fullest her call as a daughter of God. Without anything to hold her back, she was able to cooperate fully with the Holy Spirit. Through God’s favor, Mary was able to fully live the life which God had destined for her (and indeed for the entirety of creation) from the very beginning: a holy and unblemished life (cf. Ephesians 1:4). 
In the Gospel Reading, the angel Gabriel refers to Mary as blessed. It was a greeting that had a twofold meaning. Firstly, Mary WAS blessed because of what God had done (as well as what God was about to do) in her life. Mary’s achievements were not her own but rather the Lord’s doing. The Lord had chosen and destined her for a special role in his plan for creation. From the moment the Holy Spirit entered her, she ceased being Mary. She was henceforth to be referred to as the Mother of our Savior. Secondly, Mary IS blessed because of her willingness to be a vehicle of God’s grace. Mary understood that what the Lord was doing through her was not hers to keep. She was simply an instrument that God was using to make his salvation reach the earth. In her canticle of joy (the Magnificat), Mary praises the Lord for having remembered Israel his servant. 
Mary’s conception without original sin definitely plays out in the first “blessedness.” However, we see the consequences of her being spared the stain of original sin in the second “blessedness.” Mary was able to rejoice in the good fortune that had smiled upon her cousin Elizabeth because she did not have in her the self-centeredness that characterizes the rest of creation. Mary had not problem sharing her blessings with the rest of creation because she understood that we are all brothers and sisters one to another. 
Although being conceived without original sin cannot be repeated since it was unique to the mother of our Savior, the rest of humanity can still share in the graces that it bestowed upon Mary. For as St. Paul reminds us in the First Reading, the destiny which was humanity’s by right (and lost through sin) was never really taken away. The rebellion of Adam and Eve only served to temporarily put a setback in creation’s pursuit of its destiny. But since we share in the rebellion of our first parents, our eyes have been veiled to the extent of making it impossible for us to set our eyes on our destiny. It is for this that God raised up Jesus Christ born of the Virgin Mary to help rectify the situation. In Jesus Christ, therefore, God has once again adopted us and in so doing enabled us to live holy and unblemished lives just as Mary our mother did.