In my experience most of us only maintain a sense of urgency over time out of fear. That's certainly the basis of most of this advice. I've always been somewhat conflicted about using fear to motivate myself and others. I feel almost guilty that it's the best tool I've found. I feel much better about the work I do out of pure excitement, but most of the time after the initial excitement wears off, I find it's fear of failing that keeps me going strong.