Psalms 140--143 are prayers for protection. David has a host of enemies that harassed him, but they continually drove him ever closer and closer to God. I think this can be clearly seen in Psalm 140. There is also a promise here that the wicked will ultimately be destroyed. In spite of their prevalence in this life, there is coming a time when judgment will fall.
Psalm 141 is another of David's prayers for protection against being driven to sin. Psalm 142 is one of his prayers in his early life, and Psalm 143 is his penitent cry for help and guidance. This could possibly cover the time when he was being pursued by Absalom.
Note here that although David had sinned, he knew where to go for forgiveness. Too many times when Christians falter they are defeated and never seemingly come back to serving the Lord. When this happens it is a victory for the devil. David was a man after God's own heart, yet he willfully sinned. He was punished for that sin, but the point I want to emphasize here is that David never lost sight of the fact that God was a forgiving God, and in times of trouble he knew where to take his problems.
Psalm 144 is a song of praise. It is one of David's battle songs. It is likely that his army may have chanted such hymns as they moved into conflict. This Psalm is also a prayer for manifestation of the Lord's power. God is praised (verses 1 and 2) and His help sought in the light of man's weaknesses (verses 3 and 4).
