The heart of David was filled with lust for Bathsheba, murderous plans for Uriah, and rebellion against God. Throughout his life, he has been longing for a new heart, one that is filled with love for God and abhorrence of evil. The sin in his heart had caused him nothing but guilt, grief, and remorse. He desired spiritual heart surgery that could only be performed by God. He desired a spirit that would always obey the Lord. 
Since the Cross, when the Holy Spirit took up permanent residence within each born-again believer, we never need to fear that the Spirit would depart from us, as David and other Old Testament saints did. However, like David, we may resist the Spirit, quench the Spirit, or even grieve the Spirit of God. This not only breaks our fellowship with the Father but also puts a strain on our joy and steals the perfect peace of God. 
It is good news that, like David, God will forgive us our sins if we confess them. He will purify our hearts, renew our steadfast spirits within, and cleanse us from all unrighteousness. Hopefully, our new, born-again lives will increasingly conform to the image and likeness of our lovely Lord Jesus Christ as we choose the good and avoid the evil.

Dear Heavenly Father, Your grace has given us a new nature, a born-again life through faith in Christ. It is a blessing to learn from biblical saints like David who cried out to You and confessed his sins. It is also a blessing to have Your presence within me. I pray that You would show me areas of my life that grieve or quench the work of Your Spirit. Please create in me a pure heart, and renew in me a steadfast spirit, and may Christ be reflected in me. 
In Jesus's name I pray. Amen.