At the Annunciation, Mary’s “yes” to God was a joyful one. Sometimes it's hard to say yes to God, when it means doing something difficult or distasteful that might involve suffering. For those times, we have the example of the "yes" that Jesus said in Gethsemane. In the agony in the garden, Jesus knew he was entering into a cosmic struggle with Evil. He prayed to the Father to be spared that trial, but with the proviso "not your will but mine be done." It was the Father's will that Jesus go into that struggle, and he did.
But Mary's yes is a joyful one. God was offering her a great gift, and she accepted wholeheartedly. This isn't just a pious thought, but is borne out by the Gospel text itself. The word Luke uses to describe Mary's acceptance is "genoito"--let it be done. It's a form of the verb that's used only rarely in the New Testament--the optative mood. In Greek this verb form expresses a joyful willingness, even an eagerness to do something. It expresses a desire and a strong wish. So Mary said "yes" with all the desire of her heart. May we too have the same openness to accept God's greatest gift--our Savior, Jesus Christ.