"This Should Not Be Hard Between Two Sane, Consenting Adults."

I was writing about the difficulties of communication over on FetLife, and I got a sniffy comment that was essentially, “This is not a difficult thing to work out between two sane, mature adults.”
No.  It’s not difficult between two sane, consenting adults.  It rarely is.
Unfortunately, we’re also rarely entirely sane.
Thing is, sanity is a percentage.  We all have weak spots where if you poke us, we melt down.  We all have embarrassing hotspots that we reflexively conceal, whether we should or not.  You can be perfectly sane about 99% of things, but everyone has some crazy spot that triggers them into overreacting.  And everyone has some emotional issue that, when raised, makes them word not so good that communicates are mall workingfail.
And when someone skips across your insane zones – you have them – then you react in bizarre ways, and God forbid your bizarre reactions trample on your partner’s insane zone.  If you’re lucky, eventually you deal with it.  But that doesn’t make it magically “not hard” to do, especially when your monkey-brain wants to bite their face off for leaving toothpaste on the sink again.
If I only wrote essays aimed at sane, mature adults interacting with other sane, mature adults, the entirety of my output would consist of “Trust your instincts.”  But no.  I’m writing essays aimed at people who are, say, 86% sane (which is actually a pretty good sanity ratio), and dealing with someone who, up until now, has appeared to been sane 100% of the time (but we both know that’s not true).  And we’re asking what happens when either you’re walking into the minefield of your 14% craziness, or are unsure what proportion of crazy your partner has or even where their crazy-zones are.
Of course this issue is not difficult to work out for two sane, consenting adults.  No issue is.  Might as well say that “Being married is not a difficult thing to work out between two sane, mature adults” or “Raising a child is not a difficult thing to work out between two sane, mature adults,” or any other number of other flabbily unhelpful things, mainly because the definition of “a sane, mature adult” usually lines up darned closely to “someone who never has problems with common issues.”
But as for the rest of us, we’re navigating a list of unspoken assumptions with people we don’t know quite as well as we’d like (which is, actually, everybody we love), trying to see whether the insanity lies within them, or within us, or within both.
And making the blanket assumption that everyone will be as sane as you on this topic tells us that a) this place is somewhere that you are perfectly sane, and b) one of your insanities may lie in the field of empathy.