This world is part of death.
Heaven, in which there is eternal life, is the only "place" where there is life. Everything this side of the separation idea, which includes this entire universe, this planet, and all bodies, is part of the idea of an opposite to life, thus death. This is why it's a "dream of death".
Everything in this world is dead. The course calls it "a picture of the crucifixion of God's Son".
You need to realize that only at the very, very highest level, squarely centered in Heaven, is there "life", because life must be eternal life and eternity is not outside of Heaven. That means that anything "outside" heaven, which is this universe and everything in it, is not life. It's an idea or picture of death.
So even while you are "living" your life and seem to be in relative health or having a body or "half dead" or totally dead and buried, all of that spectrum of "death and dying" is death. Not just the climax. The final moment of death is just a symbol of death WITHIN a dream of death.
"There is no life outside of Heaven" literally means that every form in this world is not life. "Heaven and Earth are opposite in every way". Earth is nothing like Heaven.
When we say, that we see God in the world because God is in my mind, this is a helpful idea and can be an experience but it is not well-worded considering how many people use it. It should say, this world is an idea WITHIN God, or at least more accurately we could say, I see God IN SPITE of the world because the world is in my mind and so is God.
We must be careful not to equate this world with heaven or with God. This world is an illusion. It does NOT EXIST and it is not heaven. There is at best a reflection of heaven here in this dream, which is not the same thing as being in heaven.
This world, a picture of death, must disappear, because death is an illusion, and all illusions must disappear. This is why this world holds nothing that you want. Who could want death to be real? It is not God's creation and it is nothing like the nature of God at all.
As the course teaches, you cannot see both worlds. The body's eyes behold a world which the ego made from death, and the "spiritual eye" (the one mind) sees only heaven. The bridge, in-between the two states, or the "forgiven world", is just a transitionary state in which the world of heaven is reflected and glimpsed.
Jesus refers to Heaven as a "living world". Earth, and this universe, is not a living world. It is a dead world. It is an idea of being dead. This is why Jesus says the idea of death is the last to go, and that when the idea of death goes, the entire world goes, because the entire world is founded on the idea of death, and everything in it is an idea of death.
If you were not dead already, you would not need to achieve resurrection, and resurrection would be meaningless. But resurrection is your goal because it means you have accepted atonement and returned to life. Returned to heaven, and left the world of illusory death behind.
There is no world. This is the central lesson the course would attempt to teach. Only God's creation, God's world of Heaven, the Kingdom, which is the extension of Himself, his holy creative thoughts, as the One Son, the many sons, and the sonship, sharing love IN HEAVEN.
Where is Jesus? He is in heaven. Why isn't he in the world? Because the world is not heaven. Where will Jesus be when his body disappears? Not in this world. Where will this world be when death is fully undone? Nowhere. What will REMAIN when a world of death has been undone and disappeared, recognized as having not existed at all? The only thing that will remain is God's Kingdom, which is HEAVEN, and you are part of it and all of it. And it has nothing whatsoever to do with this universe or this planet.