|Detail from a Book of Hours;|
Walters Museum of Art
Used under Creative Commons License
To me, it's that Magnificat that is the heart of evangelization, and I think this is borne out by the way the feastday liturgy was crafted. The Entrance Antiphon is "Come and hear, all who fear God; I will tell what the Lord did for my soul." And in the Collect (opening prayer), the grace we ask above all is "that, faithful to the promptings of the Spirit, we may magnify your greatness with the Virgin Mary at all times."
To "tell what the Lord did for my soul" is to witness with praise. This is the most effective way of sharing the Gospel. (There's a real difference between "telling good news" and "setting people straight"!) But to "tell what the Lord did for my soul," when we recount it to God (or, as Mary did, "before" God), is also a form of prayer: the prayer of praise, which, it is probably safe to say, is the more neglected dimension of the spiritual life.
What does this Feast day say to you?