"When you lose your itch to do the job well for its own sake -- regardless of the client, or the money or the effort it takes..."
That bit above is from Leo Burnett's "WHEN TO TAKE MY NAME OFF THE DOOR" speech made on December 1, 1967. You can listen to it in the post below. And then come back here and add your comments about when and why you lose your itch...if at all. You can even put forth hypothesis. You'll do that?