I understand where your coming from. Seems like you have been hurt in the past and don't want that to happen again. It's ok to not want to be totally open when meeting new people and even then for must of us INFJ's it will take a long time to fully open up and then some people will just never truly know the real "us".
The only thing I would warn against is letting the past affect you in a way where you become distant and suspicious towards everyone. This can be quite toxic and in my own experience hurts oneself more than anything.
Something that helped me when I opened up to someone to much and felt bad after is that most people will forget things since they are to worried about themselves, I tested this out once and someone didn't even remember what happened which made me feel so much better.
Best of wishes to ya!