This phrase is attributed to Christopher McCandless, who died of starvation (or poisoning) in Alaska, alone. He abandoned his family, his life and lived adventures across the US until he reached Alaska with little provisions. He planned to survive out of a bag of rice he carried and the food he was able to find. He was under-prepared for the adventure and eventually died alone. His story is told in the film “Into the wild”.
The phrase might be true for most people because people are usually needy and dependent. But a truly free individual should not need to share with others to feel validated and happy.
Our need to share comes from our need to feel wanted, loved and validated, which is a sort of weakness, since it is a sort of dependence (it is a need). If an individual seeks to be strong, he/she needs to learn to be self-satisfying. There is immense satisfaction in enjoying something and not needing to share, and therefore being able to fully enjoy it. It is not an exercise of discipline that is painful; rather it becomes an even higher experience when emotional self-sufficiency is achieved, when one is able to turn happiness into something real without needing others.
Imagine an individual who travels to another planet and is unable to return to Earth. He/she sees the beauty of that distant planet but is unable to feel truly happy because he cannot share that joy. Another individual who has the same experience but is self-sufficient and fully enjoys it without feeling that “happiness only real when shared” will make more of the same experience. The latter is preferable to the former. Needing to share to be really happy is a weakness, it prevents one from fully enjoying life.
Sharing is not the problem, the problem is needing.