During a speech to the National Rifle Association during the Presidential campaign of 2008, Rudy Guiliani stopped to answer a cell phone call.
Obviously, from the tone of the conversation he had with his wife, it was much less important than the speech he was giving. Like many professionals, however, he has developed the bad habit of stopping what he is doing to do something else that just might be more important.
This flies in the face of the principle of focusing on the task at hand so deeply that one enters the Flow state. You can see from the video that he mind takes a moment to return to the task at hand, and if his wife had just told him that there was “an emergency at home,” for example, he would have shot himself in the foot by taking the call and possibly ruining the speech.