Happiness is considered very important in life Why is it difficult to define? What factors are important in achieving happiness?

Happiness is difficult to define. The meaning of happiness changes from person to person. Happiness is important in life as everyone pursue it to its own level of satisfaction. People use different mean of ways to achieve or experience happiness. It depends on the nature of personality and how that personality find itself satisfied in achieving happiness.
People go through variety of experiences and then in those moments where they define happiness in their own way. One cannot fix the definition of happiness, it is a feeling how a person feels at the moment. For example, people find happiness while helping others, there are people who have one goal in life that is serving the humanity and within this goal their lies happiness which they achieve when they help others. One of the great example Abdul Sattar Edhi, he was the most humblest and his happiness lies in helping those people who got no one in life and are alone. In contrast to this there are people who find happiness in leisure, buying most expensive cars, living in mansions, and buying anything they like are the things that makes them happy. So therefore I both cases the definition of happiness is different like poles apart from each, yet it is necessity of life.
There could be many factors in achieving or experiencing happiness, some agree that basic condition for person to find happiness is that he/she has his needs fulfilled. Basic need to live somewhere and find food to eat. Secondly there should be someone to share experience with, to live in complete isolation will make taste of happiness bitter. There could be some friends, families, or any person that one can share experience would surely make things more joyous.
Human nature define happiness, it is not something that could be defined but it is important that human basic needs are met before happiness could be achieved. It is important part of life as it brings satisfaction in life and always locked in memory to be remembered again