The Lord said David was a man after His own heart. I can see why, after reading these verses. Along with David, we lay our hearts before Him - We trust Him to reveal and expose hidden things in our soul that hinder us from walking in the freedom Jesus came to set us free from. He already made us clean in our spirit - our soul becomes full of the things we fill it with and meditate on, and is a reflection of what we believe. It is our job to keep it clean.