1. Blessed are this who keep justice. And he who does righteousness at all times. - - - First of all, not a single one of us will be righteous at all times (regardless of how hard we might try to be that way). God likes justice - as so should we.
2. And for their sake He remembered His covenant. Throughout the course of history humanity has made mistakes (and will continue to do so). Prior to the coming of Jesus, God would get angry wit humanity and, several times, thought of destroying His people - but then He remembered the covenant He had made with Noah (never to destroy all of humanity again).
3. Blessed be the Lord God of Israel, From Everlasting to everlasting - regardless of the mistakes we make, we need to be quick to repent and ask God to forgive us of our sins. We need to recognize Him for who He is - and the praise we have for Him should continually be on our lips.