The perfect peace in which God promises to keep those whose minds are stayed on him, is not a painless peace in any case of suffering.

The crushed father cannot expect a comfort which will make him forget his wandering, sinning child, or which will cause him to feel no longer the poignant anguish which the boy's course causes in his heart.

Father-love must be destroyed to make such comforting possible, and that would be a sorer calamity than any sorrow.
The comfort in such a grief, is that which comes through faith in God even in the sore pain.

The child was given to God in his infancy, and was brought up as God's child along his early years.

Who will say that he may not yet, in some way, at some time, be brought back to God?
The daily burden may then daily be laid in the divine hands.