Limits: physical, mental, spiritual, emotional.
Do you work till you drop? Give till there's nothing more to give? Exercise till the body is melting with fatigue? Does the body indicate your limits by becoming sick? collapsing? sending out unambiguous signals.
Or, do you know when the work day is over. Give only what you have available. Offer only what you have to spare. And, physical health is a given, never a worry. Nights are calm, sleep is solid.
And if you put the two in the same room? balance? complimentarity? or complete miscomprehension?