We talk a lot about burnout, but in Let Your Life Speak Parker Palmer does a good job of diagnosing the root cause of burnout in our vocation.
One sign that I am violating my own nature in the name of nobility is a condition called burnout. Though usually regarded as the result of trying to give too much, burnout in my experience results from trying to give what I do not possess – the ultimate in giving too little! Burnout is a state of emptiness, to be sure, but it does not result from giving all I have: it merely reveals the nothingness from which I was trying to give in the first place. (p. 49)