"A foolish son is a grief to his father and bitterness to her who bore him."
When children are allowed to remain in the sinful state they were born into, it produces nothing but heartache in the parents.
It is only good Christian theology that really helps parents get a handle on what is really happening in the child. The child is created in the image of God and therefore is wonderful, significant, and immortal. But because of the fall of man, every single individual since Adam and Eve has been born selfish and self-absorbed. It is this selfishness that displays itself as sins. God originally made us to prefer God's glory, others’ benefit, and then our own profit. But the sin which Adam and Eve committed plunged mankind into this upside-down world in which people naturally consider what is in it for them first.
When children are allowed to be the focal point of their own world, it reinforces the natural selfishness (sinfulness) that is already in them. It must be pointed out that it is not abnormal for children to be self-absorbed; it is exactly what is to be expected. But children, through parental training, need to expand their world to be more outward-focused and to realize that the world does not revolve around them.
Our family knows some children which are basically allowed to say anything they want, do almost everything they want, be in any mood they want. At that current pace, those sets of parents are raising fools and their unwillingness to confront their children's natural self-will is going to bring them selfish, impulsive, rebellious bundles of grief in the teen years.
and bitterness to her who bore him
It is interesting that God says that mom will be bitter against her son if her son becomes a self-centered fool in adulthood. This is usually because the child will learn how to hurt people deeply with what they say and what they do. And also the mother feels that all the sacrifices that were made during the child-rearing period are not appreciated.
It is clear that God is saying: Don't raise a fool. You can raise a different kind of child. You have 12-18 years; make sure that the things that you do cause the child to be moved beyond the self-centered world of childhood.