I’ll go first: “You have to have children when you’re young,” told to me when I was in my late 20s, with no desire to ever have kids, and no means to support them, by someone divorced multiple times with at least one adult child who does not speak to them.
Also: Responding to “How do I deal with this problem?” questions with “Oh, don’t worry about it, it’s enough that you’re even thinking about it!”
“Just don’t be germaphobic”
OH, WHY DIDN’T I THINK OF THAT!? THAT COULD HAVE SAVED ME YEARS OF THERAPY!!
People treat mental health stuff like it doesn’t exist. Like if someone has a broken arm, and everyone tells them “Just stop having a broken arm!”