Our Gemara on Amud Beis Tells us that one of the reasons why on Sunday the Cohanim from the Mishmar would not fast is because it is actually the third day since the creation of man. That is, if man was created on Friday, Sunday is the third day. There is a rabbinic tradition that pain and illness is much worse on the third day. Therefore, Sundays are not a good day to fast. 

There’s a fascinating point here, that being created itself Is considered traumatic and a kind of sickness that one needs to recover from. I think this is an astute observation by our rabbis. While life offers joy and excitement, the actual process of becoming alive and becoming born is painful and Traumatic. Can you imagine what it must be like as an infant, being expelled from the warmth of mother’s womb, first struggling to learn how to focus one’s eyes, tune into the sound, and manage the cold and the discomfort of physical life? It really is important for us to understand what babies go through, and offer them comfort and soothing.

While we were on the topic, there is an absurd old wives tale perpetuated by some frum folk based on a Chovos Halevavos (Shaar Habechina 5) that crying is good for a baby.  Here is what the Chovos Halevavos  says:

Remarkable too it is that crying, according to what learned physicians state, is beneficial to an infant. For in the brains of infants there is a humor (mucous), which, if it remained there undischarged, would produce evil results. Weeping dissolves this humor and drains it away from the brain, and thus the infants are saved from its injurious effects.

Okay, let us say that what is true in his science is still true today.  It doesn’t mean to make it a mitzvah to let the baby cry incessantly! Of course, the baby is frightened and dysregulated, and needs soothing!  What he means is, that in Hashem’s wisdom, babies have a propensity to cry, and we can all see that some crying is inevitable, and therefore it has a benefit. Fever also  is an inevitable product of a healthy immune response.  It doesn’t mean we ignore a child’s pain when he has fever!  So too, in regard to a baby’s crying.