Of her was born Jesus who is called the Christ.
The world around her must have been informed with more than its habitual loveliness, for she was gathering it all to the making of her son.
He was completely her own, utterly dependent upon her: she was His food and warmth and rest, His shelter from the world, His shade in the Sun….the four walls and the roof of His home.
It must have been a season of joy, and she must have longed for His Birth, but at the same time she knew that every step that she took, took her little son nearer to the grave.
Each work of her hands prepared His hands a little more for the nails, each breath that she drew counted one more to His last.
In giving life to Him she was giving Him death.
All other children born must inevitably die; death belongs to fallen nature; the mother's gift to the child is life.
But Christ is life; death did not belong to Him.
In fact, unless Mary would give Him death, He could not die.
Unless she would give Him the capacity for suffering, He could not suffer.
He could only feel cold and hunger and thirst if she gave Him her vulnerability to cold and hunger and thirst.
He could not know the indifference of friends or treachery at the bitterness of being betrayed unless she gave Him a human mind and a human heart.
That is what it meant to Mary to give human nature to God.
--from "The Reed of God" by Caryll Houselander (OP: Gem Fadling, Unhurried Living newsletter).