So, how do we understand the Blessed Mother's sorrow? It wasn't that the Sorrowful Mother remained emotionally downcast, depressed, or weepy. Rather, like her Risen Son, she bore the marks of his Crucifixion. He bore them on his hands, feet, and side (cf. John 20:27). She bears them in her heart and upon her soul (cf. Luke 2:35).
So, you might say, as she bore Jesus in her womb, she now bears in her heart the wounds of her suffering joined with His, the wounds of the day we all killed Him.