1. "The man who moves a mountain begins by carrying away small stones." -- Confucius 

2. "There is virtue in work and there is virtue in rest. Use both and overlook neither." -- Alan Cohen

3. "Run when you can, walk if you have to, crawl if you must; just never give up." -- Dean Karnazes

4. "Keep your face toward the sunshine--and shadows will fall behind you." -- Walt Whitman 

5. "You've got to get up every morning with determination if you're going to go to bed with satisfaction." -- George Horace Lorimer

6. "You never get tired unless you stop and take time for it." -- Bob Hope

7. "Do you think miners stand around all day talking about how hard it is to mine for coal? They do not. They simply dig." -- Cheryl Strayed,

8. "Out of suffering have emerged the strongest souls; the most massive characters are seared with scars." -- Khalil Gibran

9. "The higher your energy level, the more efficient your body. The more efficient your body, the better you feel and the more you will use your talent to produce outstanding results." -- Tony Robbins  

10. "Passion is energy. Feel the power that comes from focusing on what excites you." -- Oprah Winfrey

11. "It's not happening to you; it's happening through you. Check your thoughts and your energetic output for the answers." -- Sanjo Jendayi

12. "Now this relaxation of the mind from work consists on playful words or deeds. Therefore, it becomes a wise and virtuous man to have recourse to such things at times." -- Thomas Aquinas 

13. "Many of life's failures are people who did not realize how close they were to success when they gave up." -- Thomas Edison

14. "The more you lose yourself in something bigger than yourself, the more energy you will have." -- Norman Vincent Peale

15. "Courage is not having the strength to go on; it is going on when you don't have the strength." -- Theodore Roosevelt

16.  "Life is very interesting. In the end, some of your greatest pains become your greatest strengths." -- Drew Barrymore

17. "Have regular hours for work and play; make each day both useful and pleasant and prove that you understand the worth of time by employing it well. Then youth will be delightful, old age will bring few regrets, and life will become a beautiful success." -- Louisa May Alcott

https://www.inc.com/peter-economy/17-super-motivating-quotes-for-when-youre-feeling-unbearably-fatigued-at-work-or-anyplace-else.html