I can't imagine what it would be like to share custody of a child with an ex. I'm not saying that people shouldn't ever get divorced or split up - as Louis C.K. said, no one's ever left an amazing relationship just because. That would be horrible.
But I don't know if I'd be a big enough person to put my pettiness and anger to the side in order to have a mature, separate relationship with my ex for the sake of our children.
Or if I had to share pets with them, either. Because pets are basically fluffier versions of children that you don't have to start a college fund for, right?