It is this quick forgetting of the part you play in making your "reality" that makes defenses seem to be beyond your own control."
- ACIM - sickness is a defense against the truth... Here Jesus describes how we create sickness.
We evaluate that the truth is a threat (to our ego truth), we decide we need to defend against it, so we create a sickness by making it real and doing it to ourselves, yet making it look like we didn't choose it. Jesus goes on to say...
"But what you have forgot can be remembered".
He also says:
"Defenses must make facts unrecognizable. They aim at doing this, and it is this they do."
"And yet you have forgotten that they stand but for your own decision of what should be real, to take the place of what is real."
i.e. sickness is an attempt to obscure the truth and make it unrecognizable by associating truth with something illusory. Sickness is illusory, so regarding it as truth obscures what the truth really is.
and ie... you use sickness to convert reality to untruth and illusions to reality.
We need to then remember we did this and uncover what the truth really is, to bring about healing.