To raise children effectively, it is essential to love them. This is the most important factor in their development.
Some parents, despite loving their children, don't know how to show it: they need to smile at them, kiss them, hug them, and constantly reaffirm that love verbally. Children need this kind of evidence, and it's never superfluous or repetitive.
Conversely, when parents have a resentful and hostile feeling towards children, the children quickly pick up on these feelings even if they have not been expressed.
Children are very sensitive to everything around them and have a very keen and intuitive perception of their parents' emotional state. Children can tell when their parents are angry or worried about internal or external family factors.
If children feel they are the cause of their parents' worry or anger, they will feel extremely distressed. When this leads to punishment, it must be clear, even within the punishment itself, that the parents are doing it out of love for them.
It's like the example of a child putting a key in a socket... upon seeing this, the father slaps the child's hand and sternly warns them that it's dangerous. The underlying feeling is love for the child and concern for their well-being, while the expression of this feeling is the slap and the warning.