If ACIM is to be believed, and interpreted correctly, it is literally saying that this world is the OPPOSITE of what's real. And therefore it is completely unlike the nature of God's Kingdom. Indeed, unlike your real self.
"For this world IS the opposite of Heaven, having been made to BE its opposite. And EVERYTHING here takes a direction EXACTLY opposite to what is true."
"earth the other's sorry outcome which is Heaven's opposite in every way."
"This is the world of time, where all things end."
"Without the idea of death there is no world."
This presents a major challenge, because if the world is completely opposite to reality, truth, nature and eternal life, then every single thing in it is going to be doing things which are completely against who and what you are, against God's nature and will.
The Holy Spirit is now a spokesperson for the true nature of God's reality, and our own, and is here with us to help us to become heaven-like instead of earth-like. All of his motivation points towards eternal life rather than towards the world of mortality.
"The Holy Spirit uses logic as easily, and as well, as does the ego, except that HIS conclusions are NOT insane. They take a direction EXACTLY opposite, pointing as clearly to Heaven as the ego points to darkness and to death" "Nothing the world believes is true."
But if you'll think on this it's pretty crazy the contrast. Here we are in a world which seems very tangible and immense, and yet Jesus is saying that every single thing in it is opposite, upside-down, and backwards, from what is true. And that the body was made to deceive us into believing it is real. "The body is the instrument the mind made in its striving to deceive itself."
"Only the body makes the world seem real."
"The body is not the means by which the real world can be seen."
It would be much seemingly easier to just live a life in this world acting the way bodies act, interacting with objects, not questioning anything. Just taking everything to be verbatim as-it-is and not deceptive at all. Believing everything you see and hear.
Jesus's message is far more radical though, because if what he says is true, then fundamentally the entirety of space and time and all their contents, including all planets and galaxies, are completely false, unreal and untrue. "The only effort you need make, to give this world away in glad exchange for what you did NOT make is willingness to learn THE ONE YOU MADE IS FALSE."
So now on a daily basis, you have this task of literally questioning everything in the world, trying to recognize the world is an illusion, trying not to be deceived by everything the body shows you, trying not to identify with the body as your self, and basically denying and rejecting everything in spacetime.
That can seem very unnatural perhaps, to suggest you have to deny that the world is of God, and then deny everything about it, but Jesus does appear to be telling us to do this. That the only way out of suffering, sickness, misery and death, is to cancel out the entire seeming universe and believe none of it. That's a pretty tall order.
"This world you see MUST BE DENIED, for sight of it is costing you a different kind of vision."
Nevertheless, it's clear that this is what Jesus is instructing us to do. To exchange the belief that this world is founded on reality, for a recognition that it is nothing but a dream. A fiction of a world which is hallucinated and not really there at all. Nor does it comprise anything real or permanent or of God.
"What if you recognized this world is a hallucination? What if you REALLY understood you made it up? What if you realized that those who SEEM to walk about in it, to sin and die, attack and murder and destroy themselves, are WHOLLY unreal?"
The world is nothing. Not something, but nothing at all. It's not there. It's a pretend world, hiding the Kingdom of God. And there is nothing in the world worth keeping as a substitute for the real thing.
"Yet its nothingness IS your salvation"
"The world can ADD nothing to the power and the glory of God and His Holy Sons, but it CAN blind the Sons to the Father if they behold it. You cannot behold the world and know God. Only one is true."
"The world you see is an illusion of a world. God did not create it, for what He creates must be eternal as Himself. Yet there is nothing in the world you see that will endure forever. Some things will last in time a little while longer than others. But the time will come when all things visible will have an end.""in that instant is the world forgot, with time forever ended as the world spins into nothingness from where it came."