#ACIM lesson 248 says the following:
1 I have disowned the truth. ²Now let me be as faithful in disowning falsity. ³Whatever suffers is not part of me. ⁴What grieves is not myself. ⁵What is in pain is but illusion in my mind. ⁶What dies was never living in reality, and did but mock the truth about myself. ⁷Now I disown self-concepts and deceits and lies about the holy Son of God. ⁸Now am I ready to accept him back as God created him and as he is.
As a human body is a conglomerate of cells that has its own intelligence, so the ego consists of human patterns, habits, thoughts, and so forth.
This entity is not you, but it does a great job pretending to be so. It creates all the sufferings of the world – or, more precisely – the identification with it creates all the suffering.
That’s why in this ACIM lesson it’s told that whatever suffers is not you. Once you truly, deeply, understand this, your misery is gone.