Well, I am referring specifically to an instinctive/emotional impulse driven by the heavily ingrained belief that money does not appear or disappear from closed boxes. If you don't experience that impulse or will always be able to override it then yes, one-boxing in real life would be just as easy as in the abstract.

As per my above response to shminux, I think this effect would be diminished and eventually reversed after personally observing enough successful predictions.