There is a saying in love that what is yours is yours after all, and you can't take it away without it. How to understand?

What is yours is yours after all, no matter how much you miss it; After all, it's not yours and it won't be yours. There is some truth in this statement, that is to say, no one will take yours and slip away from you. That's not your type. Although it is said that three points are doomed, seven points depend on hard work. For love, the love you have to fight for can't wait.