One of the Greatest Miracles and Pleasures in the World is a Little Baby. Looking at one sweetens your outlook.
Even the crying, and waking up in the middle of the night and the feeding is a blessing and contributes to the joy.
As it says in Pirkei Avot / Ethics of the Fathers (5:23) “Ben Heh Heh says according to the pain is the reward.” When one “pains” oneself one receives greater satisfaction. For instance – usually who gives us the most “pain”? – our children. And who gives us the most pleasure – our children.
It is not for naught that one of the 613 Mitzvas is to “Be Fruitful and Multiply.”