After David prayed for deliverance from his enemies, his despair, physical distress, and fear of them vanished. Throughout this passage, he demonstrated his confidence in the Lord's vindication. It had been troubling for David, but now he was confident that his enemies would be defeated. The efforts they made to destroy him would come back to haunt them. Jesus promised believers victory over the world, the flesh, and the Devil.
In this Psalm, we are not informed that David's punishing circumstances were due to his sin, even though the king considered this to be the main reason for his punishment and requested forgiveness from the Lord. Even though God often disciplines His children for sin, not all of our problems can be attributed to sin. Sometimes, God uses punishing circumstances in our lives to refine us and test our devotion to Him.
Although we live in desperate circumstances and have to contend with those who falsely accuse us of all kinds of evil, we can trust that the Lord hears our prayers and cares for all of His children. As with David, God does not always remove the painful circumstances in this life, but He gives us the strength to overcome them.

Dear Heavenly Father, I thank You for the book of Psalms, which provides such encouragement and hope when we find ourselves experiencing sorrow and pain or being mocked and abused by those who hate us. You know that the time is fast approaching when You will right all wrongs and judge the world in righteousness, so help me to submit to You, resist the devil, and maintain my hope in Christ. I pray that You will search my heart and show me whether I have any sins that need to be confessed. 
In Jesus's name I pray. Amen.