The nature of reality, as defined by quantum physics, is such that all possible realities exist simultaneously at any given point in time. This is called "the superposition of all possible realities".
Also, in quantum physics, time is bi-directional - in other words, our present affects our future and our past, and our future affects our future, our present, and our past.
That said, "Here and Now" represents the intersection of all of our infinite potential future AND past realities.
It is for this reason that saying that we feel guilty, or ashamed of the past becomes as meaningless as if we said we feel guilty or ashamed of the future - one which has yet to be selected from the infinite number of those available at every given point in time. To put it another way, a singular past does not exist any more than does a singular future, since they're ALL available.
So, from a clinical perspective, why in the world would we choose to over-identify with one [past] that is painful, traumatic, or shameful when it is simply one of an infinite number of possible options from which to choose?!
Our memories are fallible, and our past a construct at best, as is our future, which "exists" only in our imaginations.
The only thing that DOES truly exist is Now - the present moment.
In quantum reality free will works forward, and backward. This is not an abstraction, but the nature of reality itself.
As such, remaining in shame or trauma now becomes a conscious choice vs. an unshakable part of our identity.
It is worth noting that every experiment ever done to either confirm or disconfirm quantum mechanics and quantum field theory (from which UTR is derived) has validated this model of reality. It is only within the past decade that we have developed apparatus capable of experimentally proving the veracity of the quantum nature of reality.