Myers indicated that good type development required conditions for developing one's preferred perceiving (S,N) and judging (T,F) processes and preferred attitude (E or I). Further, each type has a preferred dominant process aided with an auxiliary that keeps you "in balance" which needs identification.
Being clear about your preferences and what you do not prefer, followed with knowledge of appropriate use, sets the stage for learning how to use your type for effectively. For example, Thinking is for analysis and Feeling is for identifying what is of value to you. This conscious awareness of appropriate use facilitates a greater confidence in oneself. Finally, Myers further noted that specific experiences can create barriers to development.
Jung focused on the development of the unique self in his exploration of differentiation of which type is a part. You will not find instruction from Jung on type development; in fact, I suspect he would have found the idea somewhat odd--why develop just a part of a more organic whole?
If you step back and look at a larger picture of the nature of development, we know that experience is the most effective teacher. Further, testing new insights and experiencing appropriate support are essential for development to occur. There is a predictable sequence to learning new behaviors. At first there is the realization that a behavior needs to change or adjust. Then there is the effort to learn the new form of the behavior which may hav many fits and strats. Eventually, when you learn how to use the refined behavior, you realize that you are operating at a higher level of effectiveness.
So we have a couple of somewhat disconnected ideas floating around:
(1) type development requires clarity about one's type and how it works
(2) using one's type preferences effectively strengthens the type
(3) type is connected to a larger psychology within each person and changes as the organic self changes
(4) development requires learning and learning is hard work
A number of years ago I collected some data and analyzed some research about hobbies of the types and discovered that there were a good many ISTJ and ISFJ women who like hobbies like knitting, weaving, and the like. So, I wanted to test the assumption that doing activities like those who are drawn to it naturally whould have a beneficial effect. The class was astonishing--participants would show me yarn that appeared to me to be exactly the same and they could talk for 20 minutes on how different the two yarns are. Each class was a wave upon wave of awareness of that I do not pay attention to and just how much energy it requries from me to do what these other folks in the classs did as easy as breathing.
I learned to weave. My family learned to not be home on Tuesday nights when I returned from class because, as my daughter said, "you really are different when you come home from that class Dad." I've sense tested this notion of stretching to do something not typical of me and then explored what I learned. There is no way I will ever be as talented at identifying yarn qualities and weaving as the members of my class were naturally inclined to do. I could do it but it brought no joy.
I could learn the skill but that wasn't enough. I developed a new kind of appreciation for the art of weaving and the depth of richness of Introverted Sensing. But that appreciation does not translate into more competence with introverted sensing.
I think we could put all of the type functions on a continuum from:
>>unconscious, unaccessible>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>natually talented use
We would fall anywhere on the line depending on our life experience, preferences, and curent challenges as related to each of the eight functions such as Extraverted Thinking, Introverted Sensing, etc. Hopefully, what we prefer is more talented use and what we least prefer is more likely out of our awareness.
From the example I shared above, I moved my Introverted Sensing a bit further down the path of greater comfort to use but I have no desire to move up the continuum--I'm prettty functional at the moment.
We can add more skills to our preferred and least preferred processes but that doesn't mean we are necesssarily developing our type. Psychological type needs us to not only develop a greater awareness and use of our type functions but also (a) more effective at perceiving and judging functions and (b) agile access and deployment of our type functions (consciously and adaptively).
More to come on this as I've just started and I'm out of time for today.