So many success stories are attributed to a person's decision to press on against seemingly insurmountable obstacles. For many of them, it is not the final task that was so difficult, but the years of dedication to continually work and training that brought them to that final point. To work through the day-to-day grind, even without knowing if any good will come from it, is the burden that so many great people bear. It's the ability to continue on despite weariness or fatigue that brings people to greatness.
This does not mean persisting in meaningless tasks because one does not know a better way, but rather remaining determined for a just cause in the face of opposition. Working toward a higher goal can be a noble purpose in itself. Don't give up; continue to strive towards greatness.