Here is Jung's reasoning behind the idea that unconscious compensates the conscious attitude:
Because majority of people on these forums are more interested in typology, ill explain how this structure relates to functions in my understanding:unconscious behaves in a compensatory or complementary manner towards consciousness…The reasons for this relationship are:
(1) Consciousness possesses a threshold intensity which its contents must have attained, so that all elements that are too weak remain in the unconscious
(2) Consciousness, because of its directed functions, exercises an inhibition on all incompatible material, with the result that it sinks into the unconscious.
(3) Consciousness constitutes the momentary process of adaptation, whereas the unconscious contains not only all the forgotten material of the individual's own past, but all the inherited behavior traces constituting the structure of the mind.
(4) The unconscious contains all the fantasy combinations which have not yet attained the threshold intensity, but which in the course of time and under suitable conditions will enter the light of consciousness. (Jung 1960, p69)
1) Contents which the functions provide that are strong enough enter the realm of the consciousness. This doesent necessarily mean that only the most differentiated functions would be able to come into consciousness, but the difference between differentiated and undifferentiated functions that do come into consciousness, is that only the differentiated functions can be directed by the consciousness, undifferentiated functions come in the form of perceptions(intuition to be more exact). Its like directing a movie vs watching a movie.
2) Inferior function produces incompatible material for the dominant function and because dominant is the function directed by the consciousness, it inhibits inferior as it is incompatible in the view of the dominant function.
3) When it comes to functions and adaptation, we tend to adapt using our most favored functions, since that is the attitude(automatic response) towards the demands of the world. Even the most favored function is guided by the unconscious via learned(implicit memory) and inherited behavior patterns(archetypes).
4) Undifferentiated are left in the unconscious because of their low intensity(in most situations), but in the course of time and having to deal with situations that require the use of the undifferentiated functions, they start to become more strong and enter the consciousness easier and while doing so, they gradually get differentiated more and more, possibly even to the extend where they can be consciously directed with ease.
Also, if the undifferentiated functions do not get the attention from the consciousness that they require, they start to build up energy and come out in less healthy ways and possibly in inappropriate situations.