Why is Anardil's marriage to Erendis destined to fail in Unfinished Tales: The Lost Lore of Middle-earth?

Anardil's marriage to Erendis is destined to be a failure from the beginning because he loves the sea more than he loves her, and would rather spend time at sea than with Erendis (and his daughter) when he has to choose. Erendis knows this from the beginning, and she tries to change him. He loves her, and promises to stay. However, after a while, he leaves for another sea trip and she gives up on him.