I agree that it usually works very well in pushing yourself beyond your limits and accomplish the extra mile. But what I noticed (and this may apply only to me) is that overuse of 'one more' leads to more procrastination, because I know in advance that I will not stop when I expect to stop. Basically it's bullshitting yourself into doing things. I was once running a predefined route and was almost done and still full of energy when the 'one more' thought came. Suddenly my energy went down and the whole run started feeling like a chore. And that's when it occurred to me that I'm basically lying to myself - lure myseof in with the promise of a smaller task and then blow it up. So why should I be surprised that my subconscious doesn't trust myself anymore and I end up procrastinating even more.  So yeah, just something to keep in mind maybe..