Even if you reach your goals, you will always set newer and higher ones. There is never a limit, and you will never feel fully happy or satisfied until you reach them. It’s a vicious cycle.
On the other hand, there are people who set their expectations low and just go with the flow. These people tend to be different. They have that “inner” peace, look at life differently, and feel free. Even Plato agrees with us on this: “The greatest wealth is to live content with little.”