The appearance of the sickness is actually an illusion which covers up what the problem is. The sickness, the symptoms, are actually there to function as a distraction, to make you focus on the body and to make the body real. This is a protective mechanism to try to defend your ego-aligned self against a misperception of the truth.
It's not that the form of the sickness is the problem. The PURPOSE of the sickness is the problem, which is to act as a defense. There is a perceived NEED for a defense, and that manifests as physical symptoms. But the appearance of it, the physicality of the sickness, is not really the cause or the thing that's happening.
What's happening is the underlying attempt by the MIND to shut out God and to cling to the body. It just happens to CREATE symptoms such as pain and disease, in order to try to get the awareness to fixate on the body, to think that the body is very real, and therefore IGNORE the truth - to shut it out of awareness.
So sickness is an escape from reality. If someone has cancer they don't need to be healed of cancer. They need to be healed of the belief that they need cancer in order to protect them from reality. As Jesus says, when the purpose of the sickness is recognized, and when it is understood to be an illusion, it must disappear. If you had no more "use" for the sickness, and it wasn't serving a purpose of any kind, it would have no basis for the mind to keep sustaining it, and it would vanish.
So it's like, someone gets exposed to truth but their ego misinterprets it and their interpretation scares or threatens them, so they put up a "shield" of protection, which cuts them off from Life and blocks life-sustaining "energy" flowing in the system, and creates distortions in the body image. The body image then shows a sickness to symbolize the need for escape, and to provide an escape. Therefore the sickness is always a form of distraction and an attempt to make the body MORE real than the truth. Trying to make illusions more real than reality produces sickness.
If you could be convinced that you don't really have a need for the sickness because the purpose of it was misinformed, and what you experienced as a threat is not really a threat, and it's not a threat because you're not really the ego self that sees it as a threat, then you'd be willing to let it go and stop using it to protect you. You'd see no purpose in it, no need for it, and no use for it. So it would disappear.
The trouble is that once sickness is implemented, its symptoms and suffering can be so effective at distraction, so effective at absorbing your attention, so effective at making the body seem real and frightening, that you have all kinds of peripheral reactions as a whole other "layer" of experiences. You start trying to defend yourself against the defense! And that means you start to view the sickness as though you did not choose it.
Theres's a very good reason why you do not want to admit to having chosen the sickness, and it's because if you did, you'd have to own up to that and wouldn't be able to hide behind it. The sickness was made to block awareness and to shut out the truth, so if you were to admit you made it, you would not longer be able to receive its benefits of defending you.
You don't want that, so instead you shut out awareness that you made it, perceive that you did not want it or ask for it, and then launch into a series of reactions to the sickness as though it is attacking you, you want it to go away, etc... but you really don't. Not honestly. If you really wanted it to be done with you wouldn't react to it at all, you'd just admit to the ways you wanted and needed it and would drop those, having come to accept that the truth was true and your misinterpretation of the truth was invalid.
Fighting with sickness therefore is part of the huge distraction that sickness presents, and can have you spinning your wheels trying to just deal with the symptoms and discomforts. Part of you is saying you want it to go away, while another part of you - now unconscious - is actively choosing to keep it, because in the bigger picture you're still terrified of what you saw in the truth and are trying to protect yourself. It therefore frightens you to think of actually being HEALTHY, because that would mean you'd take away your PROTECTION, and then the truth would be able to attack you again. So efforts to become "well" actually can have a lot of resistance and a lot of defense against, because it actually threatens you more to become free of the sickness, IF you are still misperceiving the truth.
Perhaps a key then lies simply in the mistaken perception you originally had which seemed to show you that you needed to become sick in order to defend yourself. You need to look at what you perceived and why you perceived it. But you need to look at it with Holy Spirit or a higher perspective of truth. You need to be willing to have been mistaken. This is why you need to APPLY FORGIVENESS, to undo the ILLUSIONS that you were under that made you misperceive, creating the need for a defense. You need to disassociate from the ego identity in some way so that you do not take the truth as a threat, and do not see it as meaning that you are going to stop existing.
The primary "cause" of sickness, if you will, is the simple fact that you have bound yourself to the ego, are perceiving what IT perceives, are interpreting the truth THROUGH it, and therefore you become frightened whenever you are exposed to the truth. The truth is that the ego is not real and does not exist, and everything it believes in is false. If you are identified with it and think that it is you, then whenever the truth comes along you will be frightened that you are being attacked by it, that it implies you do not exist, that you are not real, and that's horrifying. It is a misperception, but it's horrifying. And who would not want to defend themselves against that?!
Correction is needed therefore, and a forgiveness is needed and a willingness to consider that who you are is not the ego. You need some reassurance and clarity and perspective that just because the truth says something, does not mean it is attacking you. Who you thought you were was mistaken. How you were perceiving was mistaken. What you saw in the truth was projected onto it by your own mistakes. It amounts to a willingness to accept that the truth is TRUE, and not that the truth contains evil intentions. If you can accept that the truth is true, and not false, and that what you thought was true is false, then you have the key to unlock the NEED for sickness to protect you from it.
When there is no misperception of the truth, there is no need for sickness, and you will not create it or use it.
Sickness isn't really the problem that needs healing. Sickness showing up in form is an ILLUSION, because it covers up the underlying secret ambition of self preservation, and is meant to be a distraction and a smoke-screen. That's why sickness isn't real. It's not the problem that needs to be corrected. Trying to treat the sickness or the symptoms of sickness therefore will fail.
It should be obvious that since sickness is an attempt at self-preservation, making oneself sick and likely to die in the name of self-preservation is insane.