To be found in God is the greatest place a man can be. In God there are no limitations, that is the realm of possibilities. To function in this world, you have to live with the knowledge of the laws in the world so you can use them for your benefit and not for your destruction, an example of such law would be the law of gravity, knowledge of such a law would keep you from jumpng off a cliff, thus knowing the set down laws that operate in the world helps you live a better life.
In God, the same applies, even though for one to be in God means he has come to a place of endless possibilities, he must know the laws that function in God, one of such law is the law of the spirit of life. This law functions this way: if a man comes into God under the bondage of sin and death, maybe suffering from a consequence of sin like sickness, once he gets into God that law automaticaly disables the effect of that sin and makes him free from it, thus no man in God should be sick because of the operation of the law of the spirit of life just like no man in the world should float because of the operation of the law of gravity.
The very consciousness of the operation of this law would show you the liberty you have already, thus refuse sickness in your body because just as it is abnormal for a man to float in the world, so is it abnormal for a Christian to be sick!
For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.