Whoever seeks joy in himself will be sad, but whoever seeks joy in God will always be joyful because God is forever.
(In Io. Ev. XIV, 2)
Mary was happy because she listened and kept God's word. She kept the truth in her spirit more than in the flesh of her womb.
You see creation; love the Author of these marvels. Attach yourself to the one who is essential. Love the Creator!