vs 1 - We need to see the word "confession" here as something somewhat deeper as Catholics...it incorporates all that we believe. Christ is the high priest of it all. "Confession" here reminds me of "profession" such as we do of the Creed at every mass.
vs 7-11 - these verses are extremely important (quoted from the Psalms) to Catholics. Every priest, deacon, and religious sister and brother in the world says these words every single day in the invitatory of the Liturgy of the Hours. That is how important they are to us. We can never lose faith and harden our hearts. We have a responsibility to the world to show forth the true light of Faith even in the face of adversity and in the world we live in where our Faith is ridiculed and persecuted.
vs 12+ - The author reflects here on the Psalm and its meaning to us as Christians. As we "share in Christ" through the Eucharist, his precious body and blood is given to us every mass and make us one with him - we become his Body through that Eucharist. With the graces we receive from that sacrament, how much more must we as Catholics not all into the hardening of hearts and unbelief we see in the story of the Jewish people following Moses.