The attitude of Mary shows us that being comes before doing, and to leave the doing to God in order to be truly as he wants us. Mary is receptive, but not passive. Because, on the physical level, she receives the power of the Holy Spirit and then gives ﬂesh and blood to the Son of God who forms within her. Thus, on the spiritual level, she accepts the grace and corresponds to it with faith.
She conceived ﬁrst faith and then the Lord. This mystery of the acceptance of grace, which in Mary was without sin, is a possibility for all.
—from the book Mother Mary: Inspiring Words from Pope Francis