But the best succinct version I know comes from a friend I went to grad school with: "Don't be an asshole."
Another aspect: If you think you're so smart, that you can already know everyone else's ideas are stupid and don't matter, you're probably just being an asshole.
Spotting your own negativity is a good test, but I prefer to phrase it in more self-effacing terms, "When trying to spot all the assholes in the room, I always need to find a mirror."
Another aspect: If you think you're so smart, that you can already know everyone else's ideas are stupid and don't matter, you're probably just being an asshole.