Why form bonds, and relationships, and become close with people... To have something like the full gamut of experiences in your short time on earth. It is hard

Why form bonds, and relationships, and become close with people... To have something like the full gamut of experiences in your short time on earth. It is hard to describe, but as a lifelong atheist I still think of the birth of my children as something like a transcendental experience. So intense and so many emotions. I do understand the logic of not having children is a mercy because nonbeing is less harm than existence. I think it is flawed in thinking about pain and loss in black and white terms as "bad" and therefore to be avoided. This will lead to a really narrow life. Kids love to make sand castles at the beach, and they cry when they get knocked over by the next wave. Does that mean that they should never make sand castles?