Today is a wonderful Marian feast--the Immaculate Conception of Mary. (It's also my birthday--I've always liked having my birthday on this feastday!)
Sometimes this feast is confused with the virgin birth, but they are two different things. The Immaculate Conception refers to Mary's own conception as being free of original sin. In other words, Mary had the special privilege of always being free of sin, and she was full of grace. The virgin birth, instead, refers to how Mary conceived and bore Jesus while remaining a virgin.
This is a great feast because it anticipates what we will one day be: free of sin and confirmed in grace--when we reach heaven. So today holds out for us the hope of eternal life. Unlike us, Mary always said yes to God. That didn't mean she had an easy life. She certainly had much suffering, especially when she saw Jesus die such a painful death.
Today's Gospel is Luke's account of the annunciation. It ends with Mary's beautiful words, "Let it be done to me according to your word." The Greek verb used there for "let it be done" (genoito) is a rare form of the verb. It's in the optative mood, which expresses a strong desire to do something. The grammar involved shows that Mary expressed not only a desire, but a joyful desire. Mary did not say "yes" reluctantly, worrying about what it would mean in her life and how she would explain things to Joseph. Instead, she was eager to do what God was asking of her. Mary's "yes" is a willing yes, an eager yes, a yes that overflows with her love. This isn't just a pious thought, but is based on the actual Scriptural text.
May we too, like Mary, be as eager and joyful in our service of God.