An excellent article by Jill Lepore for The New Yorker regarding burnout:

To be burned out is to be used up, like a battery so depleted that it can’t be recharged. In people, unlike batteries, it is said to produce the defining symptoms of ‘burnout syndrome’: exhaustion, cynicism, and loss of efficacy. Around the world, three out of five workers say they’re burned out.

Burnout: Modern Affliction or Human Condition