The Buddha gave a beautiful answer.
"My disciples do not regret what they might have done in the past but continue to do more and more meritorious deeds. It is not by repenting, praying and worshipping but by doing some service to others that people can overcome the mistakes that they might have done in the past. My disciples never worry about their future. They are satisfied with whatever they receive, and thereby maintain contenment. They would never say that this or that is not enough for them. That is their way of life. Therefore they are able to maintain a state of serenity, cheerfulness, and a good complexion as a result of that contenment."
Anyone can also try to maintain this cheerfulness by being contented. Should anybody ask why we cannot be satisfied in our lives although we have more than enough things, what would be the correct answer? The correct answer to give is: "We have no contenment." If there is indeed coontenment, we would never say that we are not satisfied with this or that. We cannot satisfy ourselves due to conflict between our insatiable selfish desire and the law of impermanence (anicca).
One of the best advice given by the Buddha for us to practise as a principle is 'Contenment is the highest wealth.' A wealthy man is not necessarily a rich man. A wealthy man is in perpetual fear of his life. He is always in a state of suspicion and fear, thinking people are waiting to kidnap him. A wealthy man cannot go out without a security guard, and in spite of the many iron gates and locks in his house, he cannot sleep without fear and worry.
In comparison, a contented man is indeed a very lucky man because his mind is free from all those disturbances. He indeed is rich. What then is contenment? When a person thinks, "this much is enough for me and for my family and I do not want anything beyond that," then that is contenment. If everybody could think in this way, then there cannot be any problems. When we maintain this contenment, jealousy can never cloud our mind and thereby we allow others also to enjoy their lives. If there is no jealousy, anger also cannot arise. If there is no anger, there will be no violence and bloodshed and everybody can then live peacefully.
A contented life always gives one hope and confidence. This is not idealistics.
For more than twenty-five centuries, men and women in the community of Buddhists monks and nuns have lived such peaceful lives. They had only four requisites: food, shelter, clothing and medicine. No one really needs anything else for survival. And many Buddhist householders too, have lived contentedly not allowing their greed to overtake their basic needs. It is surprising, how little we really need to be contented. Think about it.