I remember, about two or three years ago, a friend and I were walking back to my apartment when she proceeded to tell me about this thing called the "INFJ Door Slam" - a friend of hers does this. Funny thing though - I'm an INFJ, and I'd never heard of it. I couldn't even quite fathom what it meant because I hate hurting people, and I couldn't picture myself shutting someone out, even a person I didn't like. It just sounded so cruel. That is until I found myself doing it.
Some have described it as a self-preservation mechanism - an on-off switch or a pair of scissors that severs all emotional ties. Indifference.
I read one article that said after an INFJ slams the door, all interactions that follow are characterized by strange begrudging behavior. Often callus and rude.
But I would hope that other types would understand, this isn't necessarily true.
INFJs believe the best in people, often assuming that conflict in a relationship is because of something they did wrong. They try to justify your actions, rather than take issue with you. However, if your actions create a trend that suggests lack of thoughtfulness or consideration and understanding towards the INFJ, they will feel deeply hurt and rejected. It will take time for the INFJ to even consider the possibility that you did something intentional.
Once that reality sets in however, the INFJ will want to distance themselves not from you, really, but the hurt they're received. However, you caused and remind them of the hurt, so to protect themselves from such unpleasant emotions or ugly thoughts, they withdraw. Further interacts will likely lack previous depth - small talk. They probably can't make eye contact with you and conversations won't last very long.
Still... the INFJ doesn't stop caring. They can love you from afar, often asking about your well-being through mutual friends.
Aplologies go a long way, however, especially if you show repentance - truly making an effort to show understanding and sympathy. A door slam doesn't have to be permanent, but you have to knock. Be prepared for a deep conversation to follow. They've probably been stewing over the problem for a while and have a lot of thoughts on the subject they'll need to share and want you to understand.