One thing that's made the Mission: Impossible franchise so much better since Ghost Protocol is the choice to show Ethan Hunt being genuinely afraid before some of the bigger stunts.
It's played effectively for laughs; but, there's another layer to it.
As the great philosopher, Worf, once said, "A man who knows no fear, is a coward."
Taking the time to show Hunt acknowledging his apprehension and his worry that this might be the last thing that he ever does, just shows him to be a braver person when he actually does it.