One that comes to mind for me: “Whatever doesn’t kill you makes you stronger” is not always true. Maybe even only half the time! Are there any phrases you tend to hear and shake your head at?
“All’s fair in love and war”
No it isn’t you fucking sociopath
It’s not a great saying if used to defend acts (on the love side of things, that mindset can even ruin what it’s trying to “win”), but it does make sense to keep it in mind when considering possible actions of other players. If you’re fighting for someone’s love or at war, don’t assume there’s any moral limits to what others might do and that it’s thus safe to ignore those angles.