The fight happens where nobody can see it
Your Mercury speaks Aries and does most of that speaking in the 12th house, which means the fast, combative, decisive part of your mind runs almost entirely out of view. The argument gets had, won and finished, and none of it was audible to anybody.
People therefore meet somebody considerably milder than the person doing the thinking. The gap between your interior and your manner is wider here than almost anywhere, and it is not a performance.
Confrontations rehearsed and never had
You conduct the difficult conversation privately, at length, with excellent lines and a satisfying conclusion, and then say nothing whatsoever to the actual person. The rehearsal is so complete that some part of you files the matter as dealt with, which it emphatically is not. Say a shorter and considerably worse version out loud within the week, before the internal edition has fully replaced it. The energy the real conversation needed has already been spent on the imaginary one, which is why the real one keeps not happening.
The anger has nowhere to go
Irritation arrives fast and gets swallowed, since expressing it directly feels unavailable to you in a way it does not for other people with this temperament. It does not dissipate; it turns into an evening of nothing in particular. Physical output is the release valve here, and it needs to be regular rather than reserved for the days when something has actually happened.
Courage that nobody witnessed
You have done difficult and brave things in private — the decision made alone, the thing endured without mentioning it, the risk taken with no audience at all. None of it appears in anybody's account of you, including sometimes your own. Write one of them down. This position accumulates a genuine record of nerve and files it where nothing can be retrieved.
Acting alone is where you are best
Give this mind a solitary task with a real challenge in it and the output is remarkable. Put the same person in a group and the speed disappears, because the impulse gets checked before it reaches the room. Arrange your work accordingly: solo responsibility, your own decisions, reporting afterwards rather than deciding in company.
The pressure has no exit
Everything that would ordinarily be discharged in an argument stays in, so the strain here is containment rather than exertion: a jaw held overnight, sleep that arrives late after a day of nothing visible happening, a low irritability with no traceable cause. Effort taken alone is the reliable release. Something hard, most days, in your own company rather than in a class.
Saying it while it is still small
Things you do not say accumulate quietly and then arrive in one disproportionate outburst that surprises everybody including you, after which you retreat further. The practice is not restraint, which you already have, but early and unimpressive speech. One minor objection stated at ordinary volume, weekly, prevents almost all of the pattern.
You decided about them privately
Your feelings resolve internally and completely before anybody is told, so a partner can find that a decision has been made without any of the discussion having happened. That is genuinely disorienting from the other side. Say the interim version — I am working something out — because your silence during a period of deciding reads as a verdict already delivered.
You keep your distance and mind it
You hold back in groups and then experience the separateness as a lack rather than as a choice you made, and the entire cycle is invisible from outside because nobody can observe somebody not doing something. Break it mechanically rather than emotionally: one contribution per gathering, decided in advance and delivered regardless of whether the moment feels right when it arrives. The moment never feels right in this position, and waiting for it has been the whole of the problem.