"Here am I, Lord; I come to do your will."
The entrance antiphon is from the 2nd Reading(Hebrews 10):
"As Christ came into the world, he said: Behold! I have come to do your will, O God."
The responsorial psalm is "Here am I, Lord; I come to do thy will."
Obviously the Feast of the Annunciation is calling us to both remember that Jesus came to do the will of his Father and to also live this simple focus: to do the will of the Father.
The Gospel show us how. Mary is troubled and cannot understand even though the Angel Gabriel has told her, "Do not be afraid, Mary, for you have found favor with God." At the end, Mary surrenders her will to God's. "Behold, I am the handmaid of the Lord. May it be done to me according to your word."
This is the attitude God asks of me: "Here am I, Lord; I come to do your will."
Because of Mary's response, this is a great feast of Mary and reason for joy in the midst of Lent.