I think, once you found out your right type and got somewhat deeper into its meanings, type is pretty constant.
For example after the long-lasting discussions about Introversion or Extroversion, there was the conclusion that an Extroverted Type definitly can be introverted. It just depends on how he processes his information and reasoning. With P Types for example, it is always S or N what is there main function. An Extroverted Sensor can appear extroverted, when he reacts to the environment around him and the experiences gathered from the past. An introverted Sensor will be more introverted, cause it is not always clear, what he exactly saw, why for example a machine does not work anymore.
If you consider N on the other hand, a main function Extroverted and Introverted Intuition type is most likely to be nuts. Depending on what level of conversation you are faced and Extroverted Intuitor can be forced to be very introverted, cause there is just no need for his sense to pick on everything and everyone that apperead to be wrong.
I am just talking on the surface right now, do not want to write too much.
If you go on to the difference between T and F and that in combination with J. If you have someone, who deliberatly comes to conclusions, through TJ, why should he resend to a EP function for example, if not by an illness of the brain. My grandma used to say, you cant change the weather and so is TJ or FJ. That is not meant bad that is just a necessissity, no one needs a rebel EP, if there are no rules set by TJ's

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Another thing, the change from EP to TJ for example. Or to FJ. I mean consider it, concerning an ENTP that wants to become an ENTJ, I need to change everything. I have to change my way of thinking from mechanically inclined, analytical analysis, too structured organization and strategy managment. That is just impossible. I maybe can learn to think Te, but it does not intrest me and that is one crucial point. You will always stick with the thinks you can, cause you developed them because you were intrested in them in the first place. But I wont dismiss it yet, the possibility to change from Ti to Te.
Ok next step on the way from ENTP to ENTJ. My Ne needs to change to Ni and it needs to become less important for me in the order of functions. My good manners Fe needs to be abandonned and become emo-like (no heart feelings) Fi-ness. I need to become from routinized learned processes Si to become Se, world embracing and processing thinks through my 6 (or was it 5) senses. That is nearly impossible, because my intellectual life style (that means my computer addiction) already brought me to the point that I need to wear glasses and that I am a danger in traffic.
Well I have no evidence or facts to underline my theisis. I think if you have become a person and developed a personality that will never change. There are people around you, like your parents, wife (and yeah your wifes parents aswell), good friends that all would see change in you and maybe talk to you, if that is what is good for you.
If you once had the feeling or moment of thinking in your life, when you think, I am totally happy with my life, me and who I am, you will never abbandon this. Cause that is you. Any change of that wont make you happy in the long run.
And I dont mean that you have to stick with the same things all your life and being a boring fartass. I mean the way you cope with things.
Hope that was somewhat understandable
