Why does a day or two of difficult emotions, like the death of a loved one or stressful days make a person so tired?

Feeling tired ?: When u loose a loved one , u can feel down depressed , and symptoms of depression can include feeling down depressed , poor sleep or sleeping too much , decreased level of interest, guilt feeling , decreased energy, poor concentration, decreased appetite , psychimotor agitation . Or retardation.

Intense emotions or: Stress can fatigue the system. This is made worse if the person is not eating healthfully, exercising or sleeping adequately.