Our witness (or testimony) about Jesus Christ should be declarations of the facts of Who Jesus is according to the Bible. As we relate our personal experiences, we need to make sure that we define those experiences by the truths of the Bible.
If Jesus was just an ordinary man, then he is the worst sinner and heretic that ever lived! He claimed to be equal to God. How can a man claim that and be considered good?
Everything in the Old Testament form of worship pointed toward the coming of Christ. Now that He is come, the old practices need to be put away and new practices begun.