Psalm 64 is a song of lament, a choral complaint about the unfairness of life - but not just any kind of unfairness, the kind where mean, stupid, selfish people hurt other people in order to promote themselves. Based on stories I've heard about where some of you live, the kind of people you share a home with, people at the office, at school...some of those people are just plain selfish and mean. (vs3 "They sharpen their tongues like swords and aim cruel words like deadly arrows")
And here you are, trying to do the right thing by everybody, working hard to be honest, diligent, considerate of everybody, forgiving, staying out of the gossip ring, forsaking vengeance and yet...you keep getting the shaft while they get what they want.
That's how it seems, anyway.
This psalmist, like you, really needs to see justice done, that someone will do what is right and fair.
As we've heard a million times: life is not fair.
So what are we to do?
Celebrate everytime fairness does occur! Don't live as if you deserve fairness, live in such a way that you savor and celebrate it! (vs10 "The righteous will rejoice in the LORD and take refuge in him").
The psalmist credits all justice/fairness to the work of God, hence his joyful song to the Creator.
We all want to see people get their due, we need to know that at least once in awhile people who are worse then us don't get away with their shenanigans. (vs8 "He will turn their own tongues against them and bring them to ruin").
And when justice/fairness occurs - even in our own life, we breath a sigh of relief that even though this life isn't fair, God is just and he is always at work through people who are committed to being a conduit for what is good, noble, right and true.