Apostle Paul boldly declared himself as bondservant of our Lord Jesus Christ. With this mindset, he prayed that he would know Jesus more and more. To him, knowing Christ was very important since all things emanate from Him.
Apostle Paul prayed that he would have a Personal Encounter with Jesus (That I may Know Him), a Powerful Encounter with Him (and the power of His resurrection), a Painful Encounter (and the fellowship of His sufferings) and a Practical Encounter (being made conformable unto His death).
Even though Apostle Paul has had many encounters with Jesus such as his Damascus encounter in Acts 22:8-15, Jerusalem experience in Acts 22:17-21, the third Heaven’s encounter in 2 Corinthians 12:1-7, and many other encounters, he still prayed that he would know his Master Jesus.
Paul wanted to know Christ more because God (Jesus) is so vast – and infinite in His Being and incomprehensible that no one can know Him to the fullest. The closer you get to Him the farther He seems to be. The deeper you get to Him in knowledge the little you feel you know. If this great Apostle still yearned to know God after all these powerful encounters, then we have to crave for Him more.