When God forgives us, we are grateful and gratitude brings joy.
We all have known the joy of being forgiven. The best thing is that when we are sorry for our sins, God not only forgives them but also forgets them.
I think there are different kinds of joy. In the guided imagery retreat, at one moment I found myself in a meadow with a brook running through it. It was a singing brook. The stones in the water made the brook sing. Our Reverend Mother de Lescure, the Mother General when I entered, said that the stones are the difficulties we may have, but without the stones, the brook would not sing. She said that there was nothing able to take our joy away from us. I read that conference of hers when I was a young religious and have never forgotten it. So let us all be joyful and sing out our joy to the Lord. The Lord is merciful and kind - is that not reason for joy?