Mike-
I did a mindfullness course which I practice on my own.
My teacher for the course also did a mindfullness based therapy (as does my regular therapist).
The work I do with her is about those repeated pieces that come up that mindfullness by myself does not truly "work through." Often for me it is about the stuff that I cannot fully sit with by myself (though I often can AFTER I do it with someone else).
For me it is the stuff that I cannot sit with that sends me back into older more familiar places like I think you are describing.
Disclaimer on the above-some of what I am experience and working on right now is more about my eating disorder stuff then it is about my relationship stuff. No big deal if it does not resonate.