Though people feel great when they get success in their life but they are never being satisfied what they achieved. Acquire satisfaction in life never occurs. I strongly agree that people are never satisfied with what they have. They always want something more or something different. My opinion has several reasons.
First, the desires have no end. They are typically endless flow. When a person remains his childhood, he always have craving for toys, new clothes and new bicycle. These desires also grow up as the children grow up. For instance, if somebody has a good job, he wants promotion. If somebody is a rich fellow, he wants to be millionaire. Therefore, you can say that desires don't die until the person alive.
Furthermore, the life is becoming so competitive and challenging these days. If somebody gets satisfied whatever he or she has, his or her progress will be stopped there. For example, in terms of career, everybody has to fight and earn it. Today's world is so dynamic. No place for satisfied person. So, you will have to run in the race of life.
Finally, you can never achieve perfection. If you would like to be perfect, you always have to work upon it because there is no definition for perfection. So, satisfaction is required but hard to get it.
Concluding my thoughts, I can definitely say that nobody in this world is satisfied. The reasons behind it are endless desire, competitive era and hope for perfection.