When a question is large and complex, and no one really knows the answer, people often say “42”, since from Hitchhiker’s Guide, that’s the answer to the the ultimate question, which is presumably about the meaning of life, the universe, and all that, even though that is not explicitly stated in the novel.
So, the question of how to have a good marriage: well good luck! 42!
no one really knows, or no one is certain about what to say to you, because marriage is such a problematic relationship