So this is what happens.
You know when you're in a relationship, and there are parts of it that are really bad, and you get hurt? Yes, that happens to just about everyone. Maybe that was your 4th grade crush, or your college sig. other, or even one of your parents.
What those hurts and maltreatments (which are actually little brain traumas, as your brain is constantly forming and changing) do is form what's called "dissociative capsules" (search "Robert Scaer" if you want to learn more on that exactly.
So, you're technically brain damaged. Although you (and everyone else) really don't know it. Again, true for basically all of us...
And your brain always wants to heal, so sooner or later that old wound is going to move to the forefront again to try to get that healing. But what happens when you get a scrape or cut on your finger? Sure, you can leave it open, but it doesn't heal nearly as quickly or well (may get infected, takes longer to scab up, scars worse). It's best if you have on a band-aid, something to protect it as your DNA does its job and fixes the injured part. That part of you needs to be safe, in order to heal.
But back to relationships. It's not the most convenient thing, but the way this works is that, the safer you are, the more your brain will bring hurts up in order to be healed.
Which means, in practical terms, the better your relationship is, the more you'll be randomly neurotic and feel hurt over things that don't really make sense - you'll take things out of context and be just odd from time to time, as these capsules ask to be healed.
In even plainer words, you'll be, seemingly unpredictably, at your worst (from time to time) in your best relationships.
Then, if things go how your injured parts are hoping they'll go and you stay safe as the healing is happening (i.e., your partner remains wonderful and doesn't lose it too, providing a safe space for you), eventually you won't have that issue any more. Those dissociative capsules will have been dissolved and reintegrated into your overall neural pathways, or in other words, you'll have healed.
And believe you me, don't I know it. This is by far the best relationship I've ever been in, and once in a while I have issues that I never even knew I had, and that have certainly never shown up before! But, if I try to figure out exactly what's going on and where it came from (i.e. who scarred my noggin), it ends up making perfect sense, always.
Seriously, at the beginning of our time together, T would say something random and I would even freeze up - literally, no words, no movement, no response, and he'd have to sit with me and speak softly to me until I came out of it. Can you tell that he triggered some nasty stuff? And in the past, when other people had triggered (or caused) it, they'd just think I was giving them the silent treatment and leave me there, in my mental dark cage, until I scrabbled and clawed out myself, a little more injured, and certainly not healed by the power that trusting relationships innately have. By the way, this freezing up business doesn't happen any more...(yay for neural reintegration!)
So, you ladies and guys, if you're generally happy with your sig. other and once in a while just completely freak out, realize (and tell them) that it's a good thing! It means your brain recognizes that they are safe enough to try to use as a band-aid. Only a lot less disgusting.