Any emotion that you feel towards someone else, by definition, is also a reflection of something you feel about yourself.
That seems obvious (I hope) when put this way; if it’s something you feel inside of you, then the feeling comes from … inside of you.
The trap comes when we allow our ego to deny that it is us.
“I’m so angry at you, because you did this. You are the source of my anger.”
Well, no, in fact, not at all.
The source of your anger is you.
The other person simply brought it out.
So the real question is, why, or what, are you so angry about?