When you do a good deed, it's likely the recipient will go on to also help someone. This is simply human nature. As with most behavior, there's actually science behind the concept. One single act can go on to inspire many more. We've already learned about "helper's high."
It's that warm fuzzy feeling you get when you help someone. This simple concept is one reason why kindness is so contagious. Once you've shown generosity to someone and gotten that feeling of fulfillment, you want more