What's the deal with burnout?

My favorite definition of burnout is this: burnout is not about giving too much of yourself, it's about trying to give what you do not possess.
Ego ends in burnout because it's consuming resources you don't have in order to push you toward a bigger, better version of yourself.
Because a calling is an expression of your true nature, it can only end in fulfillment. You know that feeling of deep satisfaction when you're doing something you absolutely love, that's an aspect of your calling showing itself to you.

-Shelley Prevost, from "5 Ways to Distinguish Your Calling from Your Ego" (http://www.inc.com/shelley-prevost/5-ways-to-distinguish-your-calling-from-your-ego.html)