I think we all have a sense that some kind of healing can occur in relationship (hence the notion of the psychotherapy as a focused relationship). Not to infer that woundedness is a neccessary part of intimacy.... but rather that relationship is a mirror... and the better the mirror the more likely we are to bump into pieces of the self we've not wanted to deal with or feel through.
In romantic terms, when love touches a wound... there is always potential for growth or healing. The problem is that touching a wound always evokes pain. Wounds, by definition, hurt when touched.
It can be disorienting and confusing that something that feels good... can also feel so bad. The person you're coming to love can make you feel all kinds of frustration and pain. It's easy to tell them they're too much of this or not enough of that... when really it's usually that you're working against yourself to try again to bury that uncomfortable unresolved thing inside of your psyche. The burying it would work but for the fact that whether submerged or not, it's still there and always ready to be evoked by intimacy (or unconsciously projected out onto the world. This is that notion of the world as toxic threatening unsafe entity).
In simple terms, when we are putting the other into their own unresolved feelings and woundedness... the work is always counter-intuitive. The work is always to push towards the other person and not away. The choice is to embrace the discomfort that comes up. To try and understand it and work through it not as coming from your partner... but as originating from the self and your own developmental relationships. To be loved and accepted in adulthood, when your early attachment experiences involved all sorts of conditions and tight spaces... brings up a kind of greiving for all the times you needed to be loved for who you are and instead had to conform to what was available.
I guess what I'm trying to get to is this notion that pain can only be experienced in the now. Pain is always now. Its an obvious instinct to move the painful object out of your path. But much like light traveling through space and across the universe from millions of years ago... that pain can belong to the past. There's always this choice to make to throw away your partner to avoid the pain.. or to trace that light across time and space back to its origins... and then heal it. That picking away of the scar tissues... that is....