I"m not sure of the context in which you said this, so I could have it wrong. But I know that when I have said this to people in the past, part of it was usually true-- that they hadn't been through the trauma I had. Most people haven't, and I'm glad for that.

I also learned that when I said that to people, I was coming from a really "young" place, like the kind of classic teenager crying to her parent, "you don't understand what it's like to be a kid!", when of course that's the silliest thing ever, because parents of course did used to be kids, and most of us remember quite well what it was like.

Because the reality is that people can understand us even if they haven't been through it, and people can not understand us even though they have. It has nothing at all to do with having been there and usually when I used to say this, it was because I was trying to get the person to agree with me. If you don't agree, then you don't understand me. Or I was trying to get the person to specifically agree that my dysfunctional behavior really wasn't so bad.

So maybe there is something lurking underneath that feeling you have with your T that you need to resolve, but I do think that the now-healthy boundaries may move you forward faster than anything else.