This quote means that how you act determines how others treat you. If you are rude or grumpy when you interact with people, they will likely respond in the same way. On the flip side, if you show kindness and warmth, people will usually respond positively. It’s like looking in a mirror: when you look at it, the mirror reflects back the same expression that you show. Life is the same way, it is a reflection of our attitudes and behavior.