One of the great things about the Psalms is that they are the prayers of the saints, and through praying them we learn how to pray. We have in this wonderful book the prayers of David, Moses, Solomon, Asaph, Ethan, the Sons of Korah, Heman, and Jeduthun.
As is usually the case, Luther says this better than I do.
What is the greatest thing in the Psalter but this earnest speaking amid these storm winds of every kind? Where does one find finer words of joy than in the psalms of praise and thanksgiving? There you look into the hearts of all the saints, as into fair and pleasant gardens, yes, as into heaven itself. There you see what fine and pleasant flowers of the heart spring up from all sorts of fair and happy thoughts toward God, because of his blessings. On the other hand, where do you find deeper, more sorrowful, more pitiful words of sadness than in the psalms of lamentation? There again you look into the hearts of the saints, as into death, yes, as into hell itself. How gloomy and dark it is there, with all kinds of troubled foreboding about the wrath of God! So, too, when they speak of fear and hope, they use such words that no painter could so depict for you fear or hope, and no Cicero or other orator so portray them.
And that they speak these words to God and with God, this, I repeat, is the best thing of all. This gives the words double earnestness and life…Hence it is that the Psalter is the book of all saints; and everyone, in whatever situation he may be, finds in that situation psalms and words that fit his ease, that suit him as if they were put there just for his sake, so that he could not put it better himself, or find or wish for anything better. [From Psalm with Introductions by Martin Luther, translated by Bruce Cameron.]
Our Psalm for Sunday is a great example of this. Look for how the Psalmist is in great distress and trouble, yet his hope and trust is in God’s word.
81My soul longs for your salvation;
I hope in your word.
82My eyes long for your promise;
I ask, “When will you comfort me?”
83For I have become like a wineskin in the smoke,
yet I have not forgotten your statutes.
84 How long must your servant endure?
When will you judge those who persecute me?
85 The insolent have dug pitfalls for me;
they do not live according to your law.
86All your commandments are sure;
they persecute me with falsehood; help me!
87They have almost made an end of me on earth,
but I have not forsaken your precepts.
88In your steadfast love give me life,
that I may keep the testimonies of your mouth.