Someone spoke about the failure of INTJs to understand people. I used to think this way, but I realised-please see my post on emotion intelligence-that I did understand people, but that I didn't in the sense that, I can predict what a person is going to do, I know what kind of person someone is just after meeting them, I could write a whole book on some people, yet, at the end of the day, knowing say, that this girl is going to sleep with that wash-out, I'll still think "Why?" It is not so much a a lack of understanding as a feeling that someone is breaking all the rules of logical thinking, taking a way that makes no sense. It is like playing chess, you know he's going to move to g7, which will wreak his position, but you don't quite understand why he would do a thing like that.
Are INTJs weird? No, the rest of the world is mad!
I think self-confidence is inherent in the INTJ but simply needs to have its sphere of influence extended. Even when in doubt, sometimes, it is better to crush it than take a step back. It is a question of stepping on the fire or falling into the ravine.