R' Aviner:
It is essential for a baby to love and be loved. Both of these are included in one concept: Connection of love. This is essential like milk, water, and food. But we are not angels, and sometimes we express a lack of patience, lack of relationship, or lack of a smile, and the baby is disappointed and hurt.
Sometimes we do not show joy of our faces for all sorts of reasons, none of which he is responsible for: We are sick, worried about making a living, or concerned about some other problems. But the baby cannot figure out that it does not relate to him. He feels that he is the center of the world. If the parents laugh because they heard a joke, he thinks it is because of him, and he is happy. And if they are sad, he thinks they are distancing themselves from him. It is therefore always essential to smile at him, rub his skin or hair, kiss and hug him.
As we said, we are not angels, but human beings, and we make mistakes. But we can also fix them. When we do make a mistake, we must turn to him with love and explain that we will always love him. Does he understand? A little. Even if he does not understand our words, he understands our tone and our smile.
By the way, everything we said about the need to love and be loved also applies to adults.