Each of these Psalms are written by David. The first is a lament and a cry for help when David's son Absalom rebelled against his father and sought to take the throne from him. We read that episode in his life in 2 Samuel. David expresses his confidence in God's protection against any and all foes. God is able.
In many of these Psalms you will see the word Selah. This indicates a place when we should stop and consider what has just been said. Don't hurry through these readings. When the Psalms were sung, selah would indicate a place in the hymn when the singers would pause to give full effect of the words that had just been sung.
Psalm 4 begins with a plea for God to respond to David's morning call. David's psalms reflect an intimate prayer life. He is unafraid to tell God everything that is on his mind. He speaks of his sorrow and times when he feels oppressed. He expresses joy and gladness. He speaks to God of his most intimate needs and desires. Would that our prayer life would be as rich and full and intimate. Perhaps our spiritual relationship with God would be more reflective and aware of God's presence in our lives as well.
Psalm 5 is another prayerful plea for deliverance from his enemies. "Declare them guilty, O God!" Before he completes his prayer he again indicates his confidence that God will bless the righteous and protect them with his shield.
David sees God at work in everything. When he is ill he sees God's hand teaching, correcting and rebuking him. In the 6th Psalm he is asking God to be merciful to him, to heal him and keep him from his anguish. His question is our question when we do not see God's mercy at work in and around us..."How long O Lord, How long?" But always he expresses his confidence that God will hear his prayer and vanquish his enemies of every kind.
God is righteous. He is my shield and protector. He is a righteous judge. He will judge the evil and vanquish the wicked. The righteous will give thanks for the goodness of God and we will sing praise to the Lord most high.