The Burden of Suffering for Willful Sin
David prays for God to withdraw the Divine chastisement He is experiencing as a consequence of his willful sin.
He emphasizes two consequences of committing sin willfully after experiencing God’s mercy. First is Divine anger and judgement. There is a loss of fellowship with God’s presence. Second is mental anguish and physical pain or sickness. The weight of guilt for someone who has experience mercy and purity of fellowship with God can be so great as to cause physical pain and sickness in the body.
Here is the solution: “I will declare my iniquity and be sorry for my sin” (18).