An occupational hazard of caring is burnout.
Robert Wicks has written several great books on dealing with burnout and living resiliently. One of those books is "Bounce" 
What it burnout?
Burnout is a state of emotional, mental, and physical exhaustion caused by excessive and prolonged stress. It occurs when you feel overwhelmed and unable to meet constant demands. As the stress continues, you begin to lose the interest or motivation that led you to take on a certain role in the first place.
Burnout reduces your productivity and saps your energy, leaving you feeling increasingly helpless, hopeless, cynical, and resentful. Eventually, you may feel like you have nothing more to give.
Most of us have days when we feel bored, overloaded, or unappreciated; when the dozen balls we keep in the air aren't noticed, let alone rewarded; when dragging ourselves out of bed requires the determination of Hercules. If you feel like this most of the time, however, you may be flirting with burnout.
Burnout may be the result of unrelenting stress, but it isn't the same as too much stress. Stress, by and large, involves too much: too many pressures that demand too much of you physically and psychologically. Stressed people can still imagine, though, that if they can just get everything under control, they'll feel better.Burnout, on the other hand, is about not enough. Being burned out means feeling empty, devoid of motivation, and beyond caring. People experiencing burnout often don't see any hope of positive change in their situations. If excessive stress is like drowning in responsibilities, burnout is being all dried up. One other difference between stress and burnout: While you're usually aware of being under a lot of stress, you don't always notice burnout when it happens.
Stress is:
Characterized by overengagement
Emotions are overreactive
Produces urgency and hyperactivity
Loss of energy
Leads to anxiety disorders
Primary damage is physical
May kill you prematurely
Burn out is:
Characterized by disengagement
Emotions are blunted
Produces helplessness and hopelessness
Loss of motivation, ideals, and hope
Leads to detachment and depression
Primary damage is emotional
May make life seem not worth living
Source:Stress and Burnout in Ministry
and http://www.helpguide.org/mental/burnout_signs_symptoms.htm