I have previously written - a couple of times - about Father Christmas being real: more exactly of how this is true, what it means that Father Christmas is indeed real. I think this is actually a very exact explanation of the main purpose of this our mortal life - between our pre-mortal spirit life in Heaven, and the resurrected life in Heaven to come.
We came from a primal paradise as spirits, as spiritual children; and chose to become incarnated as mortals here on earth. We can sometimes recall what this life was like from that residual memory that survives into early childhood. The rest of our mortal life is about our wish to return to this (dimly recalled) Heavenly existence - but in a different and new way.
How can we get back to that?
We can't get back and stay as a final and solid state in mortal life - because mortal life is change, decay and eventually death. So all states of mortal life are intrinsically temporary - by design. But we can sometimes and briefly be there - be in Heaven again.
We get there, we are there, and we lose it; but that loss again is part of the design. We can - and should - aim to return there; again and again. And each time we overcome a different challenge to get there. And thereby we learn.
That is the main reason for this mortal life. To learn how to overcome the constraints of mortality to return, again and again, to Heaven.
This learning is temporary, so far as this mortal life is concerned (we may forget, eventually we will forget); but the point is that: we learn in mortality to benefit in eternity.
That's what it is about; we are learning in mortal life where all is temporary; but the benefits of this learning will be in our coming life everlasting.
Our major challenge is therefore to overcome The World - repeatedly, on a daily, hourly, basis.
Our task of learning is therefore to rise-back-up to that Heavenly world we once inhabited; not to sink-back-into it.
To be a parent is (potentially) to rise-back-up into childhood.
To know Father Christmas as real, as a parent, is an instance.
It is a higher state to know Father Christmas is real as an adult than as a child; because as a parent we must participate consciously in the reality of Father Christmas. We must do this by choice, and actively; freely, knowing that we do it. This is Final Participation.
By contrast, the child knows Father Christmas is real simply by unconscious, passive absorption in a social world where Father Christmas is real - this is Original Participation.
The child is immersed-in that Christmas reality; but our task in this mortal life is to rise to embrace that reality; to co-create that reality, in harmony with God.