In his book Transformed Temperaments, my husband Tim, used biblical characters as examples of the kind of "change" God can produce in any individual who accepts Him as Lord and Savior and allows Him to control his life. Peter was a superextrovert sanguine when Christ came into his life. After he was filled with the Holy Spirit in Acts 2, he did not cease being an extrovert. Instead, God was able to use his outgoing, contagious spirit to win thousands to his Lord. The apostle Paul was a strong-willed, hard-driving extrovert before he ever became a Christian. But after he was saved and filled with the Holy Spirit, he dedicated his talents to God and became what many consider the most productive Christian in the first century and, through his 13 epistles, maybe in the whole of Christianity. Likewise, Moses the melancholy and Abraham the phlegmatic were totally ineffective for God until they were empowered by the Spirit of God.
Everyone would like to overcome his or her weaknesses. The only power I know that can do that is the Holy Spirit. But it is not automatic just because you are a Christian. Change will only come about when you cooperate with the Holy Spirit.
Please read the complete book of temperaments by purchasing the book...The Spirit-Controlled Woman by Beverly LaHaye