Joy is not bound by happy circumstances or the pleasantness of the moment. Joy is not opposed to these things but joy abounds in trusting the promises of God, even in the midst of troubles.
The Magnificat, Mary’s beautiful song found in the first chapter of Luke’s gospel, is a great reminder of the power of promise. Mary lifts her praise not after water is made wine or the lame given fresh legs or deaf ears opened. Mary lifts her praise not after resurrection or ascension. Instead, the pious maiden rejoices in a day that has yet to arrive in its fullness.
Mary sees the darkness has begun to fade and knows the sun will rise. And she rejoices in the promise of what is to come.
Mary said: “My soul glorifies the Lord and my spirit rejoices in God my Savior, for he has been mindful of the humble state of his servant. From now on all generations will call me blessed, for the Mighty One has done great things for me. Holy is his name. His mercy extends to those who fear him, from generation to generation. He has performed mighty deeds with his arm; he has scattered those who are proud in their inmost thoughts. He has brought down rulers from their thrones but has lifted up the humble. He has filled the hungry with good things but has sent the rich away empty. He has helped his servant Israel, remembering to be merciful to Abraham and his descendants forever, just as he promised our ancestors.” https://www.bible.com/bible/111/LUK.1.NIV