The Four part of me is more whimsical, it softens me up in some ways. it also takes me into more intuitive places, it makes self-expression really important to me (versus just stating what I see) -- it reflects on me as a person in some way rather than being completely detached, it also leads me to feel like I need to leave some kind of mark that uniquely identifies me. it also means inside I can feel very dramatic about something -- things can become very personal to me, even while it's always nailed to the floor by the Five aspect and I don't allow myself to respond to it. But it's there and needs attention, so it can be very frustrating to experience.
I feel like Four and Five are very much at odds at time, Five is always trying to keep things to rational and stable conclusions and decision-making, but the Four demands recognition, and needs to FEEL something. The more I FEEL, the more ALIVE I feel. It doesn't matter when it's something wonderful or something horrible, it's the intensity of the experience that most matters. I mean, pain isn't great, but it's still an intense emotion and it can be wielded and channeled to make an impression on something.
So as you've got Four working herself up into everything being some kind of ultimate intense experience of good vs bad, lovely vs ugly, meanwhile you're got Five there keeping an eye on things -- processing it, keeping perspective, trying to learn something through it, and keeping Four from acting on it externally. All the drama is internalized.
(In that sense, the Nine is also a moderating force for me -- it keeps Four drama from acting out, by keeping things stable, and balanced, and trying to keep the peace. You've really got Five and Nine keeping things stable; Five brings sense to things, while Four brings the chaos and life to it. They have learned to coexist with one another rather than abusing or smooshing down each other... which is what Five used to do with Four all the time, but Four never really stood for it. To be honest, Five has realized there are some times when her rational process is being too restrictive and only Four has the drive and intensity, even the desire, to deal with something. So it's become more of a marriage now.)
I also think that the part of the OP topic that I've been most curious about is the dynamic between the natural inclination to wall off your feelings (T) and the desire to be entirely emotionally honest with yourself (4).
Well, parts of that were not a problem -- Five (with its understand of cause/effect and its quick insight) coupled with Four's ruthless honesty meant I struggled a lot with self-loathing and internally brutalizing myself and others. The "brutalizing" comes from having an unrealistic superego construct growing up, so I was never good enough and nor was anyone else, I could see every imperfection and flaw. As an adult, I moderated my perfectionism and expectations better, and so I could "forgive" a lot more even if my passion and understanding did not change. The biggest difficulty for me was honesty in the sense of "if I feel an emotion, it's okay to feel it and sometimes I even need to act on it to change my life, rather than subjecting it to excruciating rational scrutiny." IOW my happiness as a person sometimes meant accepting my passions as a reflection of truth, even if I couldn't explain them; and that it was okay to even hold personal values. For example, maybe I can't foolproof explain why altruism is better, or why freedom is better, or why kindness is better, or why I believe all people should be treated a certain way regardless of gender or skin color or culture or age or whatever else (some of these things, of course, I CAN argue for and probably convincingly) ... but where I got to in the last decade of my life is that I no longer need to explain any of it. It's stuff I "believe" and I don't have to apologize for it or cloak it all the time. I also don't need to keep apologizing for who I am, or not expect to be treated like everyone else.
So that's kind where integrating Four into a Five mindset was most obvious.