Clearly David has self-esteem issues. The guilt that drips from the verses of this Psalm is palpable. He is feeling God’s displeasure. God’s arrows have pierced David’s heart and the hand of the Lord’s discipline weighs heavy on Him. For many people today such a view of self and of God is rejected out of hand. God is loving and I am okay are the watchwords of the day. But for all our efforts at positive self-esteem, suicides are rampant, addictions are out of control, teenage girls suffer from anorexia, bulimia, and cutting themselves. Teenage boys have uncontrollable rage and anger. Marriages collapse at an alarming rate because people are miserable and trying to find themselves. And all the while the culture sings the theme from the Lego movie, “Everything is Awesome”.
We may initially recoil at David’s emotional and spiritual self-flagellation, thinking it is twisted and harmful. But look more closely and what you will see is that David emerges from His despair because he admitted his shortcomings. He let God’s displeasure sink deep. He owned his failures. And in owning them he also called upon the Lord to be merciful and to be his salvation. As a result his esteem came not from self, but from a God who said, “I know your sins and your failures. In fact they are worse than you even imagine. But I love you more than you could ever dream. You are precious to me to the point of sending my Son to die on a cross for you”.
For me to be whole and healthy I must admit my guilt and sin, daily. But I must not wallow in the mire of my sin and guilt. Instead I need to let the love God has for me lift me out of that mire and put my feet on solid ground. I cannot do it myself no matter how good it tell myself I am. I need that to come from outside. I need to embrace the love of God and rejoice that my salvation comes not from my own efforts, for they are pitiful, but my salvation comes from the King of Glory, the Lord of Lords who loves me more than I could ever know. I cry out with David, “make haste to help me oh Lord my salvation”.
O Lord, rebuke me not in your anger,
nor discipline me in your wrath!
2 For your arrows have sunk into me,
and your hand has come down on me.
3 There is no soundness in my flesh
because of your indignation;
there is no health in my bones
because of my sin.
4 For my iniquities have gone over my head;
like a heavy burden, they are too heavy for me.
5 My wounds stink and fester
because of my foolishness,
6 I am utterly bowed down and prostrate;
all the day I go about mourning.
7 For my sides are filled with burning,
and there is no soundness in my flesh.
8 I am feeble and crushed;
I groan because of the tumult of my heart.
9 O Lord, all my longing is before you;
my sighing is not hidden from you.
21 Do not forsake me, O Lord!
O my God, be not far from me!
22 Make haste to help me,
O Lord, my salvation!
Dan Lacich: Provocative Christian Living 
Love this; I think you captured the truth completely and succinctly.