We look at mountains and call them eternal, and they seem. . . but in the course of time, mountains rise and fall, rivers change their courses, starts fall from the sky, and great cities sink beneath the sea. Even gods die, we think. Everything changes.
Being a father is like directing Alien or Invasion of the Body Snatchers. It's much more difficult than directing an episode of TV. Also, directing a show or movie lasts a few months at most, parenting lasts for decades.