This false non-duality idea of "you don't have a self" is not part of ACIM itself and is only something that people have projected onto it in attempting to mis-understand it.
You DO have a self, a PERMANENT soul, which God created. There is a you in Heaven. God loves YOU and always will.
Being in ego, it really means an attempt to DENY yourself, to NOT BE yourself. The ego and the body are images of what you THINK you are, which are attempts to cover up what you REALLY are. What you really are is a permanent spirit being, a soul, a Son of God, which God created with eternal life.
We are permanently brothers in creation. In reality, God created many children and we are all equal. Every one of us has an individuality.
"God who encompasses all being NEVERTHELESS created separate beings who have everything INDIVIDUALLY and want to share it to increase their joy."
Believing that "you will end" in the atonement is really the ego's fear. The EGO will end, and the ego is not you. In fact the ego is NOT the idea of a self. It is an ILLUSION of a self, APPEARING to be a self, but is EXACTLY OPPOSITE TO THAT. It is the idea of the END OF YOU. It is the anti-christ. Which is why it leads to death.
It's the idea that YOUR SELF, which God gave you, has "become separated from" other selves. That you've been ostracized from the family. Rejected. Abandoned. Alone. It is this "separation from" the rest of God's Kingdom that is being healed in the atonement, so that you can RETURN TO being in UNITY WITH all other created beings. To return home to reunite with your brothers and with God.
The ego fears its end because the Holy Spirit proves IT does not exist. Atonement is the end of the ego. But YOU are not the ego. It's ONLY because you - your real self - has tried to IDENTIFY WITH the ego self, the "not me" fake self, that you think YOU will go down with it. You will not. In fact your sense of self is going to expand to it FULLNESS.
"The ego is the idea of selfishness. The Soul is the idea of self-fullness."
When you are FULLY YOUR SELF, you will be as God created you. When you are not being fully yourself, it's because you are rejecting some parts of existence by trying to be selfish, and simply put selfishness is what the ego is. An attempt to isolate and exclude. It is ONLY the isolation and exclusivity which ends, NOT your self. You BECAME a "separated one", but you do not have to remain a separated one. You can become rejoined with the family. "God's family".
Your real self is permanent and real. "I am not an illusion but a reality." You are a son of God, and so am I, and we will live forever in God's being as brothers."