Richelle E. Goodrich said this quote

Life works on the same principle as a boomerang. It's simple, really—what you send out you get back. A smiling face receives many smiles. Friendliness finds itself surrounded by friends. Giving hugs creates hugs. Offered help is reciprocated. In contrast, if you hurt people you will find much hurt in your life. Unkindness begets unkindness. Misery begets misery. A dour face will receive many sour looks in response. That said, it is easy to understand that if you want a happy life you must contribute to the happiness of those around you.