Loss and grief are part of life. Your parents will die. Your grandparents as well. You either die young or live long enough to see some of your own generation die before you. If you are really "lucky", you see all of your friends die.
Death is a part of life. Everyone hopes that they outlive all their children, but even if you do not, tragedies during your life do not mean that your entire life was unhappy.
In our culture. That might not be the case in every culture. Some cultures even practiced infanticide, others practiced child sacrifice. Surely it cannot universally be the worst thing or such practices could never exist.
(Modern USA infant mortality is less than 0.6%)