The myths are enwrought with curses. A curse as a twist of fate, a new thread in the fabric of the same. The curse triggers the retroactive effect of an action. Depending on the force with which I throw a large or small ball against the wall, it comes back.
What we take for granted on the physical level is ridiculed in the West in the case of fate and karma or is considered impossible. But the same forces are at work here, every action, even words and thoughts, trigger a reaction. In mythology curses can never be taken back, they can only be changed, softened.