I believe in Newton's Law of Motion that a in every action there is always an equal and opposite reaction. It is not only applicable in science but also in our attitude. Why? Let me explain.

When we do good it doesn't mean that we will receive good things in return. There is an equal and opposite reaction from people around us. It's either a praise or a bash. 

The person we usually help will make or destroy us. So never expect. Never assume. 

Just remember the law of motion.