If you don't understand this, then you're probably still stuck in the arrogant mindset that you're so amazingly unique/perceptive/miscellaneous that you can see every perspective on everything.
The human psyche builds its self-concept and its idea of the nature of reality upon certain fundamental "truths" which the self
must consider true in order to uphold the ego's self-image.
When an idea comes along which threatens these truths, it is dismissed vehemently, as a form of defense mechanism.
You cannot simultaneously hold two conflicting ideas about the truth of the universe in equal esteem, because you would not have a coherent self image.
cognitive dissonance
 
–noun Psychology .
anxiety that results from simultaneously holding contradictory or otherwise incompatible attitudes, beliefs, or the like, as when one likes a person but disapproves strongly of one of his or her habits.
Still doesn't address my issue: imitation is not a part of it; it requires changing mindsets and perceptions of different environments.
On the contrary; imitation is the entirety of it.
You can change mindsets between your four function attitudes, as none of them contradict each other. They all come together to form a complete person (or at least they should, ideally.)
But you don't (or very rarely, at least) change mindsets into completely different types or into functions that don't inherently make sense to your mindset.
If you are an Fi type, for instance, your concept of the "truth" of morality is based upon an internal standard. You seek to find that which feels harmonious and ethical to you and you alone, in the greatest depth possible, because you see morality as an idea that can only be understood by the individual, from the inside.
The competing mindset here is called Fe, which is the idea that morality cannot be evaluated without some externalized context, without a collective consensus of the informed ("the informed" in this case being the people in the cultural/familial/social groups to which the Fe user feels emotionally connected.) The Fe user seeks a broader, more widely applicable moral standard which we can all agree will govern everyone in our group, which necessitates that we sacrifice the individualized depth of personal feeling that the Fi user requires from his conception of morality.
So you may sometimes do things that the Fe users around you agree with you are moral, but if you are an Fi user, this does not constitute "using Fe" because you did for a different reason.
The Fi user did it because "
I felt it was the right thing to do, and for this reason it did not matter to me whether anyone else agreed", while the Fe user did it because, "
We felt it was the right thing to do--it was in line with the collective standard by which my group defines itself and by which I define my relationship to the group and thus my moral identity, so whether or not I personally felt it was right did not matter because my connection to the group is of greater importance and I trust that the group is a greater moral authority than my personal feelings."
The idea that you've changed from INFP to INFJ would suggest that you've completely inverted your entire concept of the nature of morality (from a self-authority to a group-authority view) on a whim.
This would require the unraveling of everything you consider important about yourself and your approach to life and would generate such enormous cognitive dissonance that such a change would destroy your very sense of identity.
It's just not that simple.
I am familiar with this thought exercise and it does not apply here. We're talking about the very building blocks upon which your whole value system is constructed. Changing type would be analogous to building a completely new ship out of completely new materials, not using the same materials to build a "different" ship.
Maybe it is; or it could be the simple solution: I change a lot.
Your ego is threatened by the idea that you aren't so smart/special/clever/unique that you are too multi-faceted not to have access to all the functions.
In reality, though, this only reveals that your multi-perspective development is at such an early stage that you have not yet accepted the ultimate limitations of perspective upon yourself.
I'm sure you change a lot, but you change within the parameters of the preferred functions of your type. If you think you are changing types routinely, you simply have not yet developed enough of a concept of the differences between types to make these distinctions accurately yet.
It's funny how dumb people (and I am not calling you dumb here) are too dumb to realize they don't know everything, while smart people are too smart to believe they do. When you find someone truly competent at anything, he'll always be the first to underrate his own abilities in areas with which he's unfamiliar.
He's perceptive enough to recognize that, while he may have attained high proficiency in one area, this implies that there is much greater possibility for development in so many other areas that he cannot possibly claim to have done so.
In short, the wise man recognizes the true extent of knowledge and is able to see by comparison that his own knowledge still leaves an enormous amount to be desired.
The unwise man believes himself to be wise because he is not yet aware of the extent to which knowledge itself expands far, far beyond the bounds of his conscious awareness.