Melancholies commonly ask, "Can my temperament be changed?" Sanguines rarely ask that question because they like themselves and like the fact that most other people like them too. Cholerics don't want to change, but they would like to change most other people. Phlegmatics are usually content to happily watch others as spectators in life.
But the bottom line is, no, your temperament cannot be changed. Happy is the woman who understands that God made her the way she is and wants to use her that way. He had a plan for you when you were conceived, and will use all your life circumstances to mild you into the person He wants you to be, if you allow Him to do so. Your weaknesses should make you realize your dependency on Him. By understanding your weaknesses, you can overcome them through the filling of the Holy Spirit. God then can use your talents to the maximum degree. Most people are so dominated by the weakness side of their temperament that they destroy their inherited strengths.
Please read the complete book of temperaments by purchasing the book...The Spirit-Controlled Woman by Beverly LaHaye