Quote from ACIM Text Chapter 6, Section 6 - The Lessons of the Holy Spirit.

A wise teacher teaches through approach, not avoidance. He does not emphasize what you must avoid to escape from harm, but what you need to learn to have joy. Consider the fear and confusion a child would experience if he were told, "Do not do this because it will hurt you and make you unsafe; but if you do that instead, you will escape from harm and be safe, and then you will not be afraid. "It is surely better to use only three words: "Do only that!" This simple statement is perfectly clear, easily understood and very easily remembered.