From a Naturopathic perspective:

Based on what I see in my practice, the majority of people experience extreme fatigue after a long period of stress. This directly applies to all of us on Biznik since owning and operating a business is one of the most stressful (and also rewarding) things we can undertake. So absolutely, our health affects our business!

It boils down to energy, productivity, and motivation, all of which are driven by a multitude of complex neurochemical reactions made up of what we eat, think, and do.

If digestion is not functioning optimally you probably are not breaking down and absorbing food very well. This can lead to amino acid deficiencies which creates an imbalance of the chemicals in the brain that affect our performance. Guess what hinders our digestive vitality? Stress!

So its a catch 22 situation! What to do about it? Take measures to help your body deal with stress when you can't change the circumstances. This includes certain herbs and vitamins that help your adrenal glands adapt to stress. Equally as important is enhancing digestion. This can be as simple as a teaspoon of apple cider vinegar in water before meals, and many other ways.

Bottom line; if you don't feel well or have boundless energy, especially after a period of stress there are a lot of ways you can improve your energy and even focus with targeted natural therapies.