The abundance of audio and video recordings of preaching today tempts pastors to listen to themselves and look at themselves. One might improve a few things that way. But in general it’s a bad idea. John Stott explains why:
If you look at yourself in the mirror, and listen to yourself on tape, or do both simultaneously on videotape, I fear you may find that you continue to look at yourself and listen to yourself when you are in the pulpit. In that case you will condemn yourself to the cramping bondage of preoccupation with yourself just at the time when, in the pulpit, it is essential to cultivate self-forgetfulness through a growing awareness of the God for whom and the people to whom you are speaking.
I know actors make use of glass and tape, but preachers are not actors, nor is the pulpit at a stage. So beware! It may be more valuable to ask a friend to be candid with you about your voice and mannerisms, especially if they need correction. An Indian proverb says “He who has a good friend needs no mirror.” Then you can be yourself and forget yourself.