A story I needed to hear

There is a wonderful Buddhist story about a woman whose son gets sick and dies. She goes to the Buddha to ask him to bring her son back to life; I will, he says, if you bring me some mustard seed from the home of a family that has not known loss. She goes from house to house but can find no family that has not lost someone dear to them. She buries her son and goes to the Buddha and says: I understand now.