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."