that I may know him and the power of his resurrection, and may share his sufferings, becoming like him in his death, (Philippians 3:10, ESV)This verse captures the essence of Paul's life.
Paul wants to know Christ. He wants to know what it is like to be filled with the same power that raised Christ from the dead and is now working in him. He wants to participate in the sufferings of Christ. And he ultimately wants to die in obedience to God the Father, the way Christ did.
One way to define Spiritual Growth is to define it as increasing in the knowledge of Jesus Christ. Living a more righteous life simply flows from this: it is a result of spiritual growth, not the growth itself.