"Only the self-accused condemn."
"You but condemn your brother of your own sins"
"You never hate your brother for his own sins but for your own"
In fact large sections of the Course really go into detail about how you put your stuff onto others, how you accuse them, how this accuses you, how you feel guiltier for this, and how you need to demonstrate your brother is innocent.
There is a very deep and simple truth in these statements.
Every time you ever believe it's someone else's fault, its your own stuff.
Every time you feel like some reaction in you is caused by someone else or something else, its really just your own stuff coming up inside you.
Every time you think someone has the power to influence you in any way whatsoever, you're mistaken because you can ONLY do stuff to yourself.
Every time you feel guilty that you have the power to do something to someone else, you are mistaken, because you cannot harm anyone.
It all boils down to this profound and life-altering fact:
Absolutely everything you are experiencing or have ever experienced is entirely contained within your SELF.
Its all from yourself, to yourself, about yourself, in yourself, as yourself. That's all.
There is no influence from others, there is no harm from others, no causes coming from others, nobody is capable of yet alone actually doing things to you against your will. Just as you are not capable of doing anything to anyone else.
Everyone is "Self-Contained". You are like a container of pure water (truth), and into that water you've spilled some oil - that you made up yourself - dark black thick oil which obscures the purity a little. So now you're walking around, still self-contained, and what you're attempting to do in an act of "ego" is to try to get rid of that oil by going outside your self containment. You're trying to give away ownership of it, trying to project it, trying to blame it, trying to shovel it onto someone else, trying to relinquish responsibility for it, and and you're trying to make out that every single time you notice the darkness in yourself it's someone else's fault for putting it there.
Nobody else has ever put darkness in you. Nobody else has ever influenced you or affected you or caused you to feel anything. Nothing.
Every single time you have a "re-action"... you're not really having a re-action to something outside your self containment. You are, instead, bringing up the dark oil inside your container and are experiencing it. And because YOU chose to bring that oil to the surface of awareness at the same time as some other person seeming to 'do something', you conveniently are thinking that they caused it. They didn't. Nobody else put that there but you and they are just reminding you that you need to clean yourself up.
Look at your life. Look at how every single time something happens you 're-act' in the belief that this something has 'caused' you to feel this way. It hasn't. You already feel this way. You just keep trying to bury the darkness out of sight so that you can escape from it. You need to learn to take responsibility for it and to transform your experience, internally, within your self containment, so that you can experience something better. You need to learn to catch yourself when you're believing and experiencing that someone or something else has put this upset into you, or caused you to feel unhappy, or pissed you off, or unloved you. Nobody has ANY power to do this. Its all you, because this is all about who you are and what you are.