Irrational Demand

When you help someone it's out of your kindness not your duty, am I right?
Yesterday Mehrdad was so angry. He said although he had helped someone but at last that person thought all it was his responsibility and even expected him more services. These people are somehow so irrational. They only see themselves and expect others to be at hand for them but never think about their own duties of having this much expectations. Anyway, Mehrdad didn't do that persons demand and because he thinks he was right ,he wasn't accused in his mind ,so yesterday passed so happily for us.
But I'm thinking about that person who must be angry all day for those irrational expectations which weren't done:D