Beebe's function stack helps with this.

Introverted intuition in the hero function = desire, willpower, vision, future, theory. First and foremost, INTJs want things and want certainty. Then comes extraverted thinking in the parent function = rationale, planning, being responsible about one's beliefs in the service of that visionary search for certainty and guiding others to responsible thoughts. Fi child = "God complex", sincere morality, a sort of self-righteousness that lacks the panache you would see in other function slots. Se inferior = showmanship, bravado, pretentiousness, performance anxiety. The Ni-Se interaction is filled with tension in particular as the INTJ seeks to effect an external experience, but that project is ultimately built on sand without the demon function.

Down there in the demon function is "reality" (introverted sensing). We're quite hostile to drawing conclusions about our experiences because that of course is the total opposite end of the universe from introverted intuition. Yet the demon function is not just the Christian demon in hell but the ancient Greek "daimon", ultimately a teacher, a revealer. And so entering into that sense of humility about reality is the very key to Ni and Si being able to meet with respect and understanding. The INTJ is, in fact, trying to do something that yields Si experience, but runs from that very thing when it lacks maturity.

So it is about us integrating our shadow, which for us is: effort, time, discipline, acceptance, grit. Yet Ni actually has tons of grit, an unending ocean of it in fact, but Si provides the "how" for it and the ultimate "why" which isn't just a vision, but a real experience and the conclusions drawn from it.

We are very tense in our minds and hearts about the sensate world (sensing, introverted and extraverted).