CLAIM: God personally created us in our mother’s womb (Ps. 139:13). Therefore, our personality and temperament were created by God. Does God change our personality, when we come to Christ?
RESPONSE: No. In fact, God doesn’t change our personality; instead, he transforms it to become more like Christ. Before Paul met Christ, he was a highly driven and willful person. In fact, he was a blood-thirsty killer, hell-bent on persecuting Christians. After Paul met Christ, God used his strong will and drive for the purpose of church planting and spreading his message of forgiveness. Later in life, God certainly made Paul gentle and broken, but he still used Paul’s personality and temperament for his glory.
Galatians 1:13 and Philippians 3:12 both demonstrate this nicely. In both passages, Paul uses the same Greek word (dioko) to describe his will and drive both before and after conversion.
(Gal. 1:13 NASB) For you have heard of my former manner of life in Judaism, how I used to persecute [Greek dioko] the church of God beyond measure and tried to destroy it.
(Phil. 3:12 NASB) Not that I have already obtained it or have already become perfect, but I press on [Greek dioko] so that I may lay hold of that for which also I was laid hold of by Christ Jesus.
Paul’s zeal and passion did not change at his conversion. He was zealous and passionate about Judaism, and he used that same zeal and passion for “pressing on” to Christ. God didn’t terminate his personality at conversion; instead, he transformed it.
 For a excellent study on this subject, see LaHaye, Tim F. Transformed Temperaments. Wheaton, IL: Tyndale House, 1971.