i can’t think of three right now but i can think of one at the present moment. and i will preface this by saying that this occasion was NOT halacha specifically, but i am just pointing it out to show something that we changed because of our yetzer hara’s gone mad:
tu b’av. girls dancing in the fields, boys picking out which one would be their wife. what do you think would happen if we would do that these days? and please don’t say it would be the end of our shidduch crisis.