I agree completely with every statement above. Usually people tell their life stories to me (which I'm usually very interested in) but I really, really hate to tell much about my private life. I just think theirs are more interesting, whilst I know mine is not boring at all as well. It's just.. hard to explain my quirks to other people.
Also, especially in stressful or emotional situations, I usually try not to show an overtly amount of emotion, because I don't think the situation is helped by that. But trust me, I feel a lot of emotions inside and my mind is racing with thoughts and feelings.
When I see someone in need of emotional comfort, I feel his/her pain, and sometimes I'd rather walk away than to put a hand on his/her shoulder, because it would hurt myself too much. It's almost a rational decision to go there and start comforting.
I like to sit on the sidelines and observe, while my mind is figuring out what is going on, especially in group dynamics or the chemistry between two persons. I think people find me very aloof when I'm doing this. While I know I needn't be, I'm also sensitive of what people think of me.
I'm quite bad at showing empathy because I'm afraid the levees will break and all my emotions will be poured out uncontrollably. In personal life, especially in relationships, I have had a few times that I cracked and went hot headed uncontrollably. Not pretty, I can tell you that.
A couple of weeks ago I had a talk with a friend of mine who has a sister suffering from depression and suicidal tendencies. I felt very bad for her and through my questions I invited her to tell more about it. Then she cracked and cried and I started apologising immediately for my questions (while trying to keep my tears in as well) but she actually said she was relieved that someone asked the right questions and that she could open up.
I still feel bad for making her cry.
Hm, should be easier to be an INFJ female than an INFJ male.