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!”
Lost out on a good job opportunity with this one. I was going to do some interview prep and someone just told me to, “be yourself, they just want to get to know you.” Yeah bullshit… didn’t get that gig and did interview prep for a different opportunity. It went incredibly well the second time around.