It is really difficult to understand INFJ since we can be a personality chameleon. We only show our true selves to the people we trust, which are not many. We are cold to the people we find fake. We're highly sensitive, so within minutes we already figure you out.
If you really want to connect to the INFJ person, be sincere. Also, don't ask us superficial questions like "How are you?". Even though you mean well, we take it as redundant.
Ok, I'm digressing.
Main point is, it is difficult to understand INFJ. We're commonly mistaken for INFP too, among other things. If you have any specific scene or question, we can help to explain further.