When you do not have enough money, your life is busy trying to get more money. Rich people on the other hand, having already enough money, start worrying about other things. I think it is in human nature to be unhappy to some extent. Its just that our worries are masked by us being busy. I mean, a person who is worried about getting money for his/her next meal has little time to worry about anything besides that, while a person who has enough money, has enough time to worry about small things. Nowadays, such problems are called 1st world problems.