He asks God to go to battle for him. He has done nothing but dole out kindness and mercy and his enemies just wait for him to stumble to point a finger and laugh.
Twice in this reading he asks God to vindicate him with His righteousness. Vindicate can mean avenge or even more importantly liberate. David is so desperate to be free from those that seek to harm him and wants God to completely liberate him from his oppressors.
David truly loves God and his Psalms are a great uplift to those who are facing trials. I think of teens being tormented at school, or the family in debt who just can't get a break--these Psalms can comfort and sustain them. While David is struggling he is resting under God's wing and trusts completely that God will deliver him...
I'll leave you with this:
3 Because your love is better than life,
my lips will glorify you.
4 I will praise you as long as I live,
and in your name I will lift up my hands.
5 My soul will be satisfied as with the richest of foods;
with singing lips my mouth will praise you.