In spiritual maturity, the opposite of injustice is not justice, but compassion. Not me against you, not me straightening out the present ill, fighting to gain a just result for myself and others, but compassion, a life that goes against nothing and fulfills everything.
The true source of joy is love -- love of God, love of beauty, love of wisdom, love of another human being, it does not matter which. It is all one love: a joyful awareness of dissolving boundaries of our ordinary narrow self, of being one with the reality beyond, of being made whole.