Sinking sand or stable ground

People will try to achieve self-validation through being the best mom, or a superior athlete, or being at the top of their field. Some will feel valuable as a person for things as shallow as beauty or having the best stamp collection in town. People will work hard and sacrifice many things to earn a sense of value and purpose in life. What happens though to the mom's sense of value when her kids turn out badly, or the beauty queen when she loses her beauty? None of these things are wrong in themselves but if they become the basis of their self worth their identity is built on sinking sand. They may not fall apart like many do, but may rebuild their sense of value on some other unstable foundation. Why does humanity work so hard to achieve a sense of value? What has caused this sense of emptiness? Should not people work from a secure sense of value instead of working to achieve value?