Here's a question: what makes all the pain and hardship worthwhile?

Are you asking for an explanation? It's quite common to hear people idealise life and romanticise everything in a way that sounds more pleasant to the ear. These kind of people tend to say things like - "Love is the answer to all problems" In retort, (for someone who doesn't believe this to be true) a pessimist may say - "If love is the answer, could you rephrase the question?" which basically means, "if love is the answer, what is the question OR I don't understand the question" It's just a clever little comeback to bring people back down to Earth. IF you were not looking for an explanation...sorry, lol but you need to define your question a bit more. As a realist, I'm not ignorant/naive enough to believe that "love is the answer to everything", but it sure does help.

Apart from the non-existence of the devil, what is the other biggest myth in the history of humankind?

Are u asking to form a question for the answer "LOVE"?