This is a most fitting prayer to obtain the grace of purity from Her who is the perfect model of this virtue and whose feast we celebrate today (Feast of the Immaculate Conception). I also added a brief reflection of Henri Nouwen on this feast.
“Immaculate Virgin Mary, I confide my chastity to your maternal heart. I ask your help to guard my senses, especially the eyes, for an unchaste eye is the messenger of an unchaste heart. Knowing my pride, I pray for that humility which invites the mercy of God. Knowing that I am human, I shall not be surprised at the urge of concupiscence, but trusting in your care I rely on your protection and all the graces that I need from your divine Son. Amen.”
In this feast it seems that all the quiet beauty of Advent suddenly bursts forth into exuberance and exultation. In Mary we see all the beauty of Advent concentrated. She is the one in whom the waiting of Israel is most fully and most purely manifested; she is the last of the remnant of Israel for whom God shows his mercy and fulfills his promises; she is the faithful one who believed that the promise made to her by the Lord would be fulfilled; she is the lowly handmaid, the obedient servant, the quiet contemplative. She indeed is the most prepared to receive the Lord.
It seems that there is no better time to celebrate this feast than during these Advent days. It is the celebration of the beauty of her who is ready to receive the Lord. It is like admiring the palace where the King will enter, the room to which the bridegroom will come, the garden where the great encounter will take place.
[Henri J.M. Nouwen, The Genesee Diary, pg. 174]