Because however truth may taste, it will always be better than lies.
Lifetime of a lie is short, though it can be made to live longer with the help of other lies. To sum it up, your truth will live and your lie will die. Which one you choose to label your life with is up to you. We may not be able to live forever, but …
It's about perspective.
It's a human tendency to want more, with less effort. Because of this, we tend not to feel satisfied no matter what we do, no matter how hard we work. We forget to cherish what we have achieved so far, and focus solely on when the goal will be completed.
When you have an honest heart, you do your best for the world. When you do best for the world, it raises you high in command for respect. Your honest effort is a true metric of productivity, not your polished skill.