Is it possible to maintain a controlled state of mind without organizing it? It will remain static by itself?
That is implausible. Emotion responds to whatever it is stimulated by. This can only change if the person has a conscious agenda that goes against the current influx of emotion. Such an agenda could only be established with Thinking.
In other words, if you think logically, you can have a mindset that runs contrary to your natural emotional reactions, if you do not, then you inevitably follow the course elected by your emotional reactions.
Fi can only remain static if and only if the external stimuli remains static as well. Environments that produce such consistent stimuli are very rare, almost non-existing.
Thus, almost in all cases Fi fails to remain static.
One may ask, what about the internal filter of valuation that inheres within Fi and not Fe. As the only difference between the two functions is that Fe emotes directly in relation to the object, yet Fi interposes an unconscious filter of emotive valuation between the subject and the object.
Should not such a filter give Fi a solid core within itself and therefore prevent it from being easily influenced by the external emotive stimuli?
Not so, because Fi in itself does not apply logical analysis to the emotive valuation, it does not have a clear idea of what this filter of valuation is. All things that lack a clear structure are malleable.
Ti people do things that appear stupid to others, but not due to a failure of rationality.
For instance you mention a single INTP may reject a woman because he is afraid of failure.
You also explain in detail how INTPs want to live a life that is consistent with the model of how they should live that they have in their head.
That is true. In other words, they have a model regarding how they should live their life which is very rigorously outlined often, and they do not wish to stray from that model.
I would imagine INTPs in the situation you describe are more recline to be taciturn not because of a fear of failure, but simply because they are afraid of stepping outside of the boundaries of their model. In many cases, all that this model includes is a requirement that all actions must be thought through as carefully and rigorously as possible.
Relationships are often fuzzy, and because they are difficult to think through carefully and rigorously, the INTP will be tempted to avoid such activities. As you mention, they avoid activities that are not consistent with their internal model concerning how they should live their lives.
It is true that such INTPs may benefit by stepping out of their model and allowing themselves to take actions that are not carefully and rigorously thought through, as for example, jumping into a relationship that does not make much sense on the outset.
However, I would argue (and would like to in tedious detail) why the long term benefits of a carefully though through choice outweigh the occassional drawbacks of such choices.
Hence, I agree with your descriptions of INTP behavior, however, I disagree that it is a mistake on their part to refuse to step outside of their model or in other words, make decisions that are not carefully thought through.
A more plausible alternative that I see is engaging in relationships where the situation is more clear.
This is easily attained in an INTP-INTP relationship, and could be attained if the INTP manages to pursuade his/her non-INTP partner to provide clarity for the current situation.
Thus, my thesis is, it is never desirable to act without having thought things through.
By no means, do not feel obligated to drop the subject, I am quite interested in your thoughts on this matter.