as a general rule, TM, you should get around 3 x 30 minute sessions a week that get your heart rate above 115bpm.
This can be in the form of a brisk walk, jog, bike ride or gym session ( or sex
)
Unfortunatley, being mentally drained at the end of the day does'nt help your body much, infact, stress is a contibutor to being physically unwell if it remains unchecked.