Having done many fasts while working, I can say it is not easy, but because I have a desk job I did ok, except for climbing stairs. I drink warm water to keep my energy level up and I ware extra layers to keep myself warm. I do deep breathing exercise twice a day, sometimes at lunch break. My energy levels are high in the mornings so I start work early and leave work early. I do not know if you have that choice or your energy levels are high in the morning or evening.