I enjoyed this quote by Paul David Tripp from an article I read for a counseling class:
It is never the loudness of our voice, the power of our words, the drama of the moment, the creativity of our illustrations, the strength of our vocabulary, the specter of our threats, or the grandeur of our gestures that causes a turning within people. Gentleness flows from knowing where our power lies. God can use whispered words to produce thunderous conviction in a heart. Yes, we want to think and speak well, but only because we want to be useful instruments in the hands of the One who does bring change, not because we trust our skills to produce it. (“Speaking Redemptively,” Journal of Biblical Counseling, Spring 1998)
Nothing we can do or say can change people. Only the Holy Spirit brings change, working through us to minister to others.