You've already been given lots insights.
My understanding of the mirroring phase is;
BPD's lack a defined or consistent sense of self so they are constantly seeking this in others.
When they find a suitable partner / host they attach to us in a desperate attempt to share our sense of self. They do this by mirroring back an idealised image of our self image - how we want the world see is (false self). Strong, loyal, clever, capable
Whatever qualities we most value and want to project.
For many of us this idealised self, or false self was a coping mechanism or armour that we developed to protect ourselves from childhood injury and vulnerability.
It's not to say that we may not have any of these qualities but for a while BPDs almost embrue them and us with a divine fire of perfection.
For us (and there are reasons why we end up these relationships) this mirroring / idealisation of how we want the world to see us (not how we actually are) is incredibly powerful and addictive
Depending on our narcissistic traits we not only feel that we've finally met someone who can see us for who we really are (or want to be) - we feel that we're even better than we ever imagined.
Either way this mirroring fills a deep need or emptiness in us.
But it's not real
Eventually when the relationship deteriorates, and it always does (engulfment, fear of abandonment, unstable sense of self and all the other dynamics which define a relationship with BPD) they began to devalue us.
And this glorious reflection of our idealised self (which was never real) begins to crack.
This conversation is helping my understanding so much! I definitely had to come to grips over the last year with my projected self vs. my REAL self... .I didn't realize I had been hiding so much beneath an exterior of what I wanted to be and what I wanted others to think I was... .God has been faithful to reach beneath the shell and start peeling all those fake layers away... .to reveal what I really am, and allow me to actually start pursuing becoming better and better FOR REAL! Add a uBPDh to the mix, and it has been a very long, chaotic journey! I do trust though, that everything happens for a reason, and I AM GOING TO BE better and stronger for it, in the long run, by God's grace!
Thank you all for sharing your insights! <><