When you are laboring for others let it be with the same zeal as if it were for yourself.

- Confucius

We do have a zeal for laughter in most situations, give or take a dentist.

- Joseph Heller

All enterprises that are entered into with indiscreet zeal may be pursued with great vigor at first, but are sure to collapse in the end.

- Tacitus

Zeal will do more than knowledge.

- William Hazlitt