When IS ENOUGH .... enough?

That is what I am struggling with in my mind these days. How much longer can I truly hang on at my job before I'm burned out or "let go". I work so very hard everyday and hit the ground running but it never seems to be quite enough. I keep thinking about the Moral Issues course I took awhile back and wonder if staying on there is what will bring me true happiness and a sense of well being. I can say in all honesty that I am feeling a bit overwhelmed and uneasy these days. Like I'm waiting for the other shoe to hit the fan. I'll hang in awhile longer.