Introverted Intuition - Ni (INFJ, INTJ)
Nis constantly wonder and guess in their head - they do this so often that they often don’t even realize that they are doing it. It more or less becomes a part of them. Nis easily get lost in the mind and are thus very introspective, and often pull out ingenious ideas and insights. They view life more globally than any other type, striving to never let themselves forget about the big picture. Nis constantly shift their perspectives, and view and understand things from different angles and in different ways.

Under extreme stress Nis become paranoid and overly withdrawn. Their inferior function jumps them, and they become overly interested in details and obsessed with physical pleasure. They become slaves to childlike impulses, sometimes ruining themselves with their decisions in the process.

Nis confidently trust their intuitions, insights, ideas, and inspirations - often no matter what others say. Their thoughts become part of who they are. They don’t need to rely on others, and they enjoy time to themselves. Their strong independence is a good thing, but they also have a natural suspicion about others and need to learn to trust them (INTJ’s in particular).

Nis prefer to think things through as completely as possible and dislike it when others come to quick, simplistic conclusions. Nis are known to get frustrated with others. INTJ’s are more likely to show this than INFJs, but nonetheless it is there, and often strongly felt. Nis need to remind themselves that they are extremely rare and should be proud that they see things that others don’t. Nonetheless one can certainly understand their grievance with what sometimes seems like the shallow, ignorant ways of the world.

Nis continually think about the future, what it may hold, and how what they are currently doing with their life affects it. Nis are too often hypersensitive to contingencies, possibilities and implications. To the Ni, anything is possible and could happen. Some Nis focus too much on those “coulds” and become worrywarts. Nis need to develop their auxiliary function to keep them in touch with the reality of the external world. When Nis don’t use their other functions, their unique visions turn to far-fetched crackpot theories, and their confidence turns to downright obstinacy.

Another source of frustration for Nis is their difficulty articulating their complex views and intuitions. However, when they are able to do this, the result is typically both impressive and impacting.

More on Introverted Intuitives:
Take pride in their strong perseverance, drive, and will power.
Can be sensitive to and easily overwhelmed by external stimuli
Often think of things that others don’t
Need intellectual stimulation
Aren’t afraid of the complex - they often prefer it.
Least common dominant function

[Source: http://www.famoustype.com/Ni.htm]