“Sickness is but another name for sin. Healing is but another name for God. The miracle is thus a call to Him.”
Sin is a label. It is the label that the ego thought system has put on behavior it deems wrong. The behavior is part of an image in the world, and as such it is a projection of the quality of mind content. As long as you use the word “sin”, you keep yourself locked in the idea that something “out there” is amiss and should change. But it is your own mind content that has projected a misunderstanding into a disturbing image to begin with, and so the work of release should start within. Once the misunderstanding clears, the image will start to dissolve. Sin does not exist and the word sin is a misnomer.
And so it is with sickness. Sickness is a projection of a misunderstanding onto the face of reality. When the misunderstanding clears, the image will start to dissolve and Creation in its perfection will become visible again.
A miracle is a correction. It is the correction of a misunderstanding regarding your true nature. You are not the body, and neither sin nor sickness can define who you are or what you are about.
Full text of Workbook lesson 356 in ACIM
(See also Illness as a Mirror)