Quote from A Course in Miracles Text Chapter 29 - THE AWAKENING.

T-29.II.8. Sickness is a demand the body be a thing that it is not. 2 Its nothingness is guarantee that it can not be sick. 3 In your demand that it be more than this lies the idea of sickness. 4 For it asks that God be less than all He really is. 5 What, then, becomes of you, for it is you of whom the sacrifice is asked? 6 For He is told that part of Him belongs to Him no longer. 7 He must sacrifice your self, and in His sacrifice are you made more and He is lessened by the loss of you. 8 And what is gone from Him becomes your god, protecting you from being part of Him.