Sometimes we find ourselves doing just that. I have been running on empty for several days. Taking inspiration anywhere I can get it. I am sure I am fight a flu bug but I need to rally. Some people ask me why I do not just stay home--I do not always have that luxery. I have a client counting on me and a trial date looming. So even though I am running on empty I am still running.
The clients deserves the best I have to give even when I do not feel like I can. What makes me great at what I do is that when push comes to shove I am still going to keep at.
So when you are running on empty what keeps you going; money, the client, your own determion.