“I am never upset for the reason I think.”
The last word “think” relates to the thoughts of the ego mind, mentioned yesterday, regarding lesson 4.
Per definition, any thought that may occur to you as the reason for your upset, anger, worry, concern, etc., cannot have been inspired by your higher self (the Holy Spirit in ACIM’s terms) and therefore it is a random thought, a thought of the ego mind. It has derived from the label you have assigned inadvertently to the thing or person that seems to upset you. When you strip the person or situation of that label, what is left is Creation-as-is.
So whenever you feel upset, worried, frustrated, angry, etc., you now know that the person or thing “out there” is not the reason. They can never be. You are only having an ego thought that they are the reason. Now you understand how little you can trust that thought. That thought is not truly yours, as it has not come to you through your inner being. On the contrary, it is caused by the labels that are still active in your mind and that this training is helping you to release.