From the book The ACIM Mentor Articles, August 7, 2007:

Everyone comes into the world to be separate from God. But you, _____ (fill in your name), did not make this choice personally. A part of God seemed to decide to be not-God (ego) and seemed to fragment into many distinct identities (egos) to make it seem that God’s Oneness was overcome. Your seeming individuality is a part of that part that seemed to make the decision to be not-God. But seeming isn’t reality. You are still One and you are still Part of God. The perception of personal or individual is what you are awakening from.

In this world, because the mind is split, the Sons of God appear to be separate. Nor do their minds seem to be joined. In this illusory state, the concept of an "individual mind" seems to be meaningful. It is therefore described in the course as if it has two parts; spirit and ego. (C-1.2) 

There is no “my” ego or “your” ego because all that is not-God is equally unreal. If a blue cup was filled with orange juice and a red cup was filled with orange juice would one of the cups hold something other than orange juice just because the cups looked different? Distinct bodies and personalities do not make the content of ego any different from one form to another. When you single out one ego for “love” and another for condemnation you are making some egos more real to you than others. You are making separation from God real to you. Forgiveness overlooks the error of the perception of separation from God no matter where it appears and without concern for form.

The Holy Spirit judges against the reality of the ego's thought system merely because He knows its foundation is not true. Therefore, nothing that arises from it means anything. He judges every belief you hold in terms of where it comes from. If it comes from God, He knows it to be true. If it does not, He knows that it is meaningless. (T-9.VII.7)

There is only one error. There is nothing more to know about ego than that it is not-God. And being not-God it is nothing.

What is the ego? Nothingness, but in a form that seems like something. In a world of form the ego cannot be denied for it alone seems real. Yet could God's Son as He created him abide in form or in a world of form? Who asks you to define the ego and explain how it arose can be but he who thinks it real, and seeks by definition to ensure that its illusive nature is concealed behind the words that seem to make it so. (C-2.2)