1....The title is, “Praise, to David himself.” Praise to Christ Himself. And since He is called David, who came to us of the seed of David, yet He was our King, ruling us, and bringing us into His kingdom, therefore “Praise to David himself” is understood to mean, Praise to Christ Himself. Christ according to the flesh is David, because He is the Son of David: but according to His Divine Nature He is the Creator of David, and Lord of David. “I will exalt You, my God, my King; and I will bless Your Name for the age, and age upon age”. You see that the praise of God is here begun, and this praise is carried on even to the end of the Psalm....Now then begin to praise, if you intend to praise for ever. He who will not praise in this transitory “age,” will be silent when “age upon age” has come. But lest any one should in any otherwise also understand what he says, “I will praise Your Name for the age,” and should seek another age, wherein to praise, he says, “Every day will I bless You”. Praise then and bless the Lord your God every day, that when single days have passed, and there has come one day without end, you may go from praise to praise, as “from strength to strength.” No day shall pass by, wherein I bless You not. And it is no wonder, if in your day of joy thou bless the Lord. What if perchance some day of sorrow has dawned on you, as is natural in the circumstances of our mortal nature, as there is abundance of offenses, as temptations are multiplied; what, if something sad befall you, a man; will you cease to praise God? Will you cease to bless your Creator? If you cease, you have lied in saying, “every day,” etc. But if you cease not, although it seem to you to be ill with you in the day of your sorrow, yet in your God it shall be well with you....
2. “Great is the Lord, and very much to be praised”. How much was he about to say? What terms was he about to seek? How vast a conception has he included in the one word, “very much”? Imagine what you will, for how can that be imagined, which cannot be contained? “He is very much to be praised. And of His Greatness there is no end;” therefore said he “very much:” lest perchance thou begin to wish to praise, and think that you can reach the end of His praises, whose Greatness can have no end. Think not then that He, whose Greatness has no end, can ever be enough praised by you. Is it not then better that as He has no end, so neither should your praise have end? His Greatness is without end; let your praise also be without end....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)