If you are worried this will be a bunch of geometry, do not fear. No math here.
Instead of math, create an action formula that helps you recognize YOUR signs of fatigue. Fatigue comes from excess. It doesn't have to be physical activity. Mental fatigue triggered by stress is real. What contributes to your fatigue? Keep a journal and note your energy levels during the day. Here are some examples:
Do you feel better leaving work if you have cleaned off your desk and organized your email?
Do you need to take a quick walk to clear your head after making multiple challenging decisions?
Does procrastination lead to more stress?
Does organizing relieve any stress?
What tasks or people disrupt your flow?
Do team activities give you energy or drain you?
Build a roadmap that can help you recognize and reduce your stress factors.
My formula looks like this:
Use a To-Do list + declutter daily + stand up and move every hour + batch and schedule distracting tasks = more peace for me