As salt that has lost its savor is good for nothing but to be cast out and trampled under foot, so parenting that has lost its joy results in a family trampled under foot. As parenting without training is chaos, training without joy is tyranny. A soldier can endure the mud, blood, and pain of war by fantasizing of past or future joys, but a child without joy is a lost soul. A mature wife may cope with a joyless marriage by consoling herself in the hope of afterlife, but a child cannot so resign himself. A husband may deal with a joyless marriage by losing himself in the rewards of occupation or hobby, but a child has no outlet that can compensate for loss of relationships.
Relationships are a part of the adult world, but relationships are all the world to a child.
An adult without relationships may be a successful careerists, a reader, a hobbyist, a loner, etc., but a child without relationships is emotionally ill. Where there is no joy there is not even friendship. The other extreme of joy is bitterness. If Christ were joy, Antichrist would be bitterness. No matter the skill or technique, as a painting done in bitterness leaves its scars on the canvas, so parenting done in bitterness will leave its strokes on the canvas of the soul.