I recently taught on this subject for Sunday School, and its also our discussion day topic. While preparing for this discussion I came across this from Dr. Martyn Lloyd-Jones:
"Let me put it like this: God, who is sufficiently concerned about me to send his Son to die on the cross of Calvary for me, is not going to let me down when any difficulty or temptation faces me. My dear friends, there is nothing for you to fear! You belong to One of whom we are told that all power has been given to him over all flesh. You are in the hands of the Lord Jesus Christ if you but knew and realized it, and he controls everything. He controls every human being, all the affairs of nature, he is even controlling the devil himself. All power is given unto him, thrones, dominions, principalities and powers are subject unto him, so you need never fear! You and I have but to realize that we are in those mighty hands, that that strong arm is engaged on our behalf, that all flesh under his power, and that all authority in heaven and on earth has been given to him." (Lloyd-Jones, David Martyn: The Assurance of Our Salvation : Exploring the Depth of Jesus' Prayer for His Own : Studies in John 17).