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!”
tho to be fair “change your pillowcase” is probably a decent bit of advice for a lot of teen boys in particular. I knew a lot of guys in college who only washed their sheets once a semester. 🤢 It’s the “Have you tried turning it off and on again?” of acne advice.