I think I have so many quotes that I like, but "Look at the mirror first" is probably one of my favorites. It tells us to do self-introspection whenever we can before we judge others. I think it helps me avoid stubbornness, arrogance, and other negative traits that limit me. It's really hard to apply and do consistently since we need to be aware of every bias, personal value, sociological construct, and so on. Not to mention how social media encourages people to jump to conclusions easily.