Your baby may not smile or coo at you during her/his first hours/days of life. My definition of a “happy baby” at this time is a “comfortable baby.” When s(he) becomes a little older, your “comfortable baby” can magically turn into a “happy baby.”
They need to be calm and relaxed to nap well. They may fuss when hungry or wet, but excess crying usually portends some bodily discomfort. Suspected fascial tightness would require a session of Gillespie Approach–Craniosacral Fascial Therapy.
In a perfect world, this work would be been done minutes after birth and throughout the first 24 to 36 hours as needed. Leaving the hospital on the second day, they would be calm, relaxed, and without pain to sleep/nap well.
The hospital work would also allow the entire gastrointestinal system to function optimally. Proper nursing includes good latching on, sucking, and swallowing. In order for infants to thrive in life, they need to suck, swallow, and breathe well, too. They also need to keep their milk down (reflux).
Their food needs to be broken down (digestion), nutrients passed into cells (assimilation), and energy created for the body to function (metabolism). Fascial strain needs to be released in the stomach, pancreas, liver, and gallbladder for optimal function. If your baby has gas/indigestion, these organs may be tight.
Finally, newborns need to poop well. If they do not have a bowel movement every day, fascial strain may compromise the normal peristalsis of the intestines.
I believe that a “comfortable baby” is the first step towards being a “happy baby.”