How to understand "I have nothing, but I own everything"?

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One night, I was watching a Singapore tv play. A role gave a gift with a scrip to her girlfriend. He wrote such message in that scrip: "I have nothing, but I own everything." The girl couldn't catch his meaning. He explained later but I forgot what he said. A few days later, when I encountered difficulties in my carrier and life, I felt so sad. I even decided to give up my attempts. It seemed like I lost all and only my tired body and disappointed soul left there to laugh at me. However, all at once the scrip poped up and a sound of "I have nothing, but I own everything" resounded for a long time. I was shocked and awaken. I remembered that when I was born I even didn't wear any clothing. And then I grew up, earned many things such as money, love, knowledge, marriage etc. If someone who ever had nothing could become "rich", why can't he re-build his life? Maybe I missed something. More we have, more we worry. Because we have, we worry about losing. If we don't have any, it is unnecessary to worry so we can live in a natural spiritual realm. We will become happy just like we were small kids. When we happy, we own the world. So, ignore or give up one thing, then we will gain better results.