Goes around, comes around

Once upon a time, a guy called Newton discovered one very important thing by watching an apple falling down from a tree. Through this simple fact, he created the gravitational theory, which is about the attraction between two objects. As a result, he found out that every thing that goes up, comes down.
Newton's law of gravitation says that every action has a reaction. Therefore, as the same way, every choice you make in your life will have a consequence. Some people believe we pay for any action we do in this life; others think that we still have another life to pay for that, or to have a second chance. Religions dictate different ideas about it, but I particularly believe that all the things happen in only one life.
By talking about "goes around, comes around" I mean that we reap every thing we sow, and I am not talking about revenge, but about consequences. So if we "plant" good things, we will probably "harvest" good things. That's why all the efforts we do in life are worthy: sooner or later, the reward will come, even if it happens in a long run. Very often people do not honor good actions, so we need to do them without expecting prize in return. Then, when the good result comes, we'll be taken by surprise, and this will remind us that it was really worthy to sow those good actions.