Whenever you get really mad at someone, and you want to accuse them of being all sorts of things - call them all sorts of names...
Well, think of what you want to call them, and then imagine calling yourself the same things...
Turns out, in a LOT of cases, that's what you're calling yourself. You are the things you are accusing that person of.
For instance, you think someone is vain, jealous, childish, boring, fucked up, mean, lazy, petty, whatever. Look at yourself, and you will find you ARE these things, and you are getting mad at the other person because you ARE these things. And you don't WANT to be these things. And you were probably looking to the other person to help you NOT be these things, because you first thought the other person was NONE of these things. That other person is just a straw man, and an excuse for you not dealing with your own issues. You just got too close, you got each other mixed up, and now you want change, but it isn't happening, and you are impatient, and you want to move on, so you get mad. And the last person you feel like looking at is yourself. I have to admit, this has worked on me, and I don't like it when I try it. But it did at least motivate me to be honest with myself, and to keep trying to work on the relationship. To give the other person more slack.
Now, I'm not saying this always works. Because there are definitely some assholes who deserve to be mad at. But it does work sometimes, and it gives you a chance to try to work things out. But if you keep trying over and over, and find that this stuff is really true about the other person, and not about you, then it's time to move on. You are not a fool, and you should not let the other take advantage of you.
Now, there are games you can play to PRETEND the other person is the one to blame - by NOT looking at yourself; by setting up situations; by gossipping; by expecting false proofs from the other person, etc. - which can make this all moot. You can get mad and think you're right, even when you're completely wrong. That's called lying to yourself. If that's what you want to do, ok, but don't be surprised if some people give up on you.
It's an ongoing effort. And, usually, "no one ever is to blame". We just get tangled up in relationships that produce bad results, and make us unhappy with who we are. We can change that sometimes. Sometimes we can't. And, again, I'm not saying this lttle trick is always true. But it's something everyone should consider.
But, I'll add, beware of those who would blame you for their own sins.
As Emerson said, the unexamined life is not worth living.
Neither is it worth sharing.