I've doorslammed three times in my life [note: actually four, but one was so effective I forgot it for a moment]. It has always been out of self defense with a person who I could not stay open to without being hurt. Twice it was actually mom-friends who are toxic people and who blamed my children and myself falsely for serious things. I had to shut myself off in those relationships, and as JennyDaniella says below, go completely stone-cold and entirely disengaged from them. The purpose is to a) send an unmistakeable message with a gigantic boundary, and b) to avoid continued and repeated pain to myself caused by that person.
I completely sever my emotional connection to the person, take them entirely off my radar, actively avoid them, choose not to make eye contact or conversation if we are in the same place, act like they don't exist. It is effective as self-protection. It's also incredibly sad and I wouldn't ever do it except as a last resort. It is the only recourse left when you're so emotionally connected to everything around you that you can't turn it off at will. So you turn it off permanently, which is the door slam.
So two were mom-friends...
One of the moms' kids was severely bullying one of mine last year. Even after administrators got involved, the mom would not acknowledge the situation or address it with her daughter, AND then (insult to injury) continued to act nicey-nicey to me as if nothing had happened and as if we should still be friends. When I called her on it, she aggressively blamed my child and me, and it took me only one second to choose to disengage permanently from them. I avoid the mom (and her child) and will not engage with them. I communicated clearly that I was done and then just shut myself off to her.
The other mom was several years back, and there were multiple incidents involving her kids emotionally hurting mine, and also the mom being vicious about me behind my back, and I just felt I had to cut her off and erase her from my life. Same thing - I shut myself off to her, ignore her, don't engage with her, avoid her in public, etc.
Am I sad about it? No. I'm 100% done. Stone cold. It doesn't stress me out at all - it's a relief - because I no longer have any connection to either of them.
The third time was my XH, who left me for one of my closest friends about 8 years ago. I tried to be empathetic, compassionate, collaborative about the separation at first, even through my pain. But everything I tried to do right he turned against me. It was hideously toxic and painful. So I doorslammed. Which means the same as above - I don't chat with him, we communicate only minimally and in writing not talking, I avoid him, and I made it absolutely clear that I would not tolerate being in contact with his GF. It allows me to interact with him as minimally as necessary - you can't coparent without some basic interaction - without engaging with those feelings and hurting myself over and over.
Oh, I realize his GF is the fourth. You just don't go after your close friend's husband the moment he indicates that he's planning to leave her. You don't do it. SLAM. I cannot tolerate someone like that in my life ever again. Such betrayal earns no second chances.
I don't have any intention to ever repair any of those relationships. They hurt me; it's not mine to fix and they are too far gone to be able to make amends. I don't believe I would ever reverse a doorslam. It's the last resort, and to me it's a sort of emotional exile of that person that can only be done - it can't be undone.
I have a good friend who is known in our local music circles and who suddenly and seemingly inexplicably cut ties with his brother several years back. His brother is also a local musician and they used to play together all the time. Now they do not speak and it was initiated by my friend. I feel certain my friend is an INFJ and I also feel certain that this was a classic doorslam. I don't think most people understand what that is, so they don't get why the two brothers don't speak, but I get it. I don't know what his brother did, but I am quite sure it must have been thoroughly intolerable to my friend to push him to doorslamming his brother.
My guess is that INFJs are emotionally connected/perceptive/open in a way that we have great difficulty modulating, and because we can't shut down our awareness and openness easily, this last resort method is the most effective way to permanently shut off a toxic channel to protect ourselves.
I know I've doorslammed when I stop feeling in relation to that person. The only exception has been residual pain from my divorce, but it lessens over time. I think if I could 100% cut him out of my life it would work better, but we still share custody of minor children, so those wounds get prodded regularly. But the doorslam has been otherwise quite effective (and shocking to him, but he seems to have accepted it and matches my lack of engagement).
