«عُمْرِ الرَّايِبْ مَا يِرْجَعْشْ حَلِيبْ»

Some changes run in one direction only. Once milk has naturally thickened and soured, nothing restores it to its earlier fresh state, so the image stands for any situation that has passed a point of no return and cannot be reversed.

The saying expresses firm doubt that a lost condition can ever be recovered. Its emphasis falls on the permanence of the change rather than on regret over it, treating the earlier state as simply gone.

Suitable when someone hopes a changed situation, spoiled arrangement, or altered state will revert. It works as a blunt, homely reminder that the transformation is final and that the earlier condition will not come back.