This is from Mary:the Church at the source by Cardinal Ratzinger and Von Balthasar.
Reflections on Luke 2:19 .
Found it interesting talking about Mary pondering in her heart.
…There it is said that Mary "kept’, “held together”, and “placed together” all these words (=happenings) “in her heart”. The Evangelist here ascribes to Mary the insightful, meditative remembrance that in the Gospel of John will play such an important role in the unfolding of the message of Jesus in the Church under the working of the Spirit. Mary sees the events as “words”, as happenings full of meaning because they come from God’s meaning-creating will. She translates the events into words and penetrates them, bringing them into her “heart” – into that interior dimension of understanding where sense and spirit, reason and feeling, interior and exterior perception interpenetrate circumincessively. She is thus able to see the totality without getting lost in individual details and to understand the points of the whole. Mary "puts together “holds together” – she fits the single details into the whole picture, compares and considers them, and then preserves them. The word becomes seed in good soil. She does not snatch at it, hold it locked in an immediate, superficial grasp, and then forget it. Rather the outward event finds in her heart space to abide and, in this way, gradually to unveil its depth, without any blurring of its once-only contours.
There is an analogous statement in connection with the scene centering on the 12 yr. old Jesus in the Temple. The first stage is “they did not understand the saying which he spoke to them” (Lk 2:50) Even for the believing man who is entirely open to God, the words of God are not comprehensible and evident right away. Those who demand that the Christian message be as immediately understandable as any banal statement hinder God. When there is no humility to accept the mystery, no patience to receive interiorly what one has not yet understood, to carry it to term, and to let it open at its own pace, the seed of the word has fallen on rocky ground; it has found no soil. Even the Mother of God does not understand the Son at this moment, but once again she “kept all these things in her heart” (Luke 2:51). The Greek term for “keep” here is not precisely the same as the one Luke uses after the scene with the shepherds. Whereas the latter emphasizes more the aspect of “together”, of unifying, contemplation, the former stresses the element of “through” of carrying the word to term and holding it fast…