The Golden Rule. Do unto others as you would have them do unto you. In other words, treat others how you’d like to be treated. This is solid advice and covers most day-to-day actions. For example, you wouldn’t want your stuff stolen, so you refrain from stealing others’ stuff.
I think there’s a corollary to this saying, and I actually first encountered it through one of those job training programs I had to complete for my internship this summer. The corollary is to treat others how they would like to be treated.
I think this is very relevant and addresses the nuances of different personalities and backgrounds. For example, I personally don’t need a lot of checking-in or micromanagement when I do work, but others might. So if I’m a mentor to someone who prefers more involvement, it helps to treat that person not how I’d like to be treated in that scenario, but how that person would like to be treated.
Applied on a wider scale, this saying encourages people to recognize that everyone is different, and to make the effort to understand where the next person is coming from.