Are there any pieces of cultural wisdom you've found to be untrue?

Last night I got to see a live Q&A session with Dan Savage (a brilliant sex columnist, and much more). He argued that two closely held cultural stories we tell each other are, for the most part, myths:

(1.) That if you’re really in love, monogamy is easy and you don’t have any interest in other people, and

(2.) That you should never have to do something you’re uncomfortable with in bed—sometimes you have to bite the bullet and do something you might not want to for your partner. (He is not arguing that you don’t have the right to say no to a sexual partner, he is just advocating for more flexibility and openness to experience).

For the most part, I think cultural folk wisdom tends to be dead on—for the most part, honesty really is the best policy, you really should treat people the way you want to be treated, and so on. I would be interested to hear your experiences with one or both of these ideas that Dan Savage challenged, and I’m also wondering if you can think of other cultural myths that many people buy into that you haven’t found to be accurate.