But that doesn't mean that we shouldn't attempt to reach the moon or Mars or to send rockets outside our solar system. Unless we reach for the moon, our accomplishments will be severely curtailed. Unless we give whatever we do a 100% effort, we never know what CAN be accomplished.
The same is true of our personal lives. If we hold back and don't stretch and learn and take risks and try new things we will never know what we truly can accomplish.
Today - shoot for the moon in some aspect of your life. Look beyond what seems possible and see if setting your goals a bit higher might serve you well.