The concept of happiness is a very sensitive, turbulent and impermanent feeling, because it can be ruined at any time, especially for people who give care about beloved ones and even for distant others. Happiness can be affected by many factors and at any time. These factors are various from a person to another. Some people claim or maybe they really feel happy when they do whatever they want to do. Selfishness is an enough factor to make them feel happy regardless of other things that must have been considered along the way. Such people don't know what happiness means as they also don't know what sadness means.