This couplet needs to be pondered over and over; for a whole lifetime is not sufficient enough to digest this knowledge.
Whenever happiness has disappeared from your life, look deeper and you will see it is because of the desire. And all that we desire is happiness!
No person, animal or creature desiring unhappiness is ever born, never has it happened before and never will it happen in the future.
When your small mind gets tired of running here and there, of wandering everywhere, it reaches a conclusion, "My desires have killed my happiness".
Thus a person who has conquered his desires in called "mahavira".