"You will never know that you are co-creator with God, until you learn that your brother is a co-creator with YOU."
What this tells us also is that this DREAM was co-created with brothers, there is NOT just one dreamer.
It also means, we need to learn that other people have THEIR OWN free will, and their own choice, and have to choose atonement for THEMSELVES.
This also means, that you choosing atonement for YOUR self does not automatically heal or undo or force anyone ELSE to accept it. And this in fact is why you then become part OF the atonement PLAN and are to help others!
It also means that you are clearly NOT responsible for the choices of other free-willed beings and must RESPECT THEIR FREEDOM in order to respect your own. That means you have to ALLOW others to choose whatever THEY want to choose, and that's not something the ego is very happy about because it frequently wants to run other people's lives and tell them what to do and accuse them of doing something they should not be doing.
Free will also indicates that even if you purify your perception and becomes true perception, it WILL NOT prevent you from seeing or perceiving the MISTAKES that other people are freely choosing. Nor does it make it impossible for you to see their bodies, nor does it make it impossible for you to see that they are SICK.
All it means is that you now RECOGNIZE CORRECTLY what you are perceiving, which means you recognize the person's sickness is FALSE instead of TRUE. Seeing sickness as false does not mean seeing no sickness at all, it just means you are not deluded into thinking it is a demonstration of truth, and so it is not REAL to you. You thus can still discern that other people are calling out for help and that you CAN then help them.
Many people have come to believe that there is only one dreamer and therefore one perceiver, and therefore anything happening to other people is "part of your dream" and so part of your own mind and so something YOU are putting there.
This then suggests if you change your mind it must somehow make other people's problems disappear. But I think if you are honest you will admit, THIS HAS NOT HAPPENED, and it is simply because your PERCEPTION OF the world has become more accurate and true, you are not perceiving LESS and other people STILL HAVE INDEPENDENT FREE WILL.
You have to recognize and allow other people to have the TOTAL FREEDOM to choose for themselves, OTHERWISE you cannot acknowledge your own total freedom to choose atonement for YOUR self. This is why we have to learn to let other people have the freedom to WILLFULLY come to God by their own choice, and not force them into it. God does not coerce and nor should we.
This is also why it can be difficult to try to OFFER teaching to others, because generally speaking, any "student" is inherently UNWILLING, and that is why they NEED to learn, and yet the teacher is offering something to them. In order TO teach it, willingness has to happen somewhere in the student, and sometimes to bridge that gap the teacher "tries" to "get" the student to see what they are seeing, and that can potentially become a slippery slope of demand or coercion. No-one learns against their will, and this is why the Course says not to terrorize your students. It's a very fine line between offering something to those who are WILLING, versus trying to get someone to see sense when they are UNWILLING. It is only when students are unwilling that conflict happens. And then you have to let go and allow them to have their beliefs. This is respect for their free will. They are not "supposed to" "get it", against their will.