What is the best advice you ever received?

The best advice I had ever recieved is from my father. I was having some problems with my friends. The problem: One of my friends(which I would just call A) do not like the attitude of another one of my friends. (I would just call this B) Everytime A will always tell me that B is not very nice. I was getting a little bit annoyed by A. I was also scared that A and B would fight and end up being enemies. So I talked to my father. My father told me that I should talk to A and tell her not to talk bad things about B because we should be friends not enemies. After doing that, my father told me to encourage A to be friends with B and I also need to be friends with both of them. I did all the things that my father instructed me to and I had no problems anymore. That is the best advice I had ever recieved.