Excellent point.
To expand on your analysis a little, I was listening to an interview Nolan did with Elvis Mitchell on The Treatment, and Nolan mentioned that Bruce takes his father's advice of "Don't be afraid" too literally. Through Batman, Bruce attempts to live without fear-- or in the words of Ra's Al Ghul, "to become more than a man"-- and bring justice to Gotham. This, of course, occupies the first two films.
At the start of TDKR, we see that he has essentially done that-- and yet, personally, he is miserable. Fighting the forces that killed his parents and left him an orphan has resulted in poor health, the death of Rachel, Alfred's leaving the Manor, and a general detachment from the world.
By putting the mask back on to fight Bane in the first act of TDKR, Bruce deludes himself into thinking that to be successful again he must defeat fear (his enemies) as he did before. As Rachel notes in TDK, despite Bruce's statements to the contrary, he needs to be Batman. It is quite literally his way of masking his problems.
In prison, however, Bruce finally learns that fear is on some level necessary to rise out of the pit, and in the short term, save Gotham. At a personal level, this lesson is fully realized in the final scene when he is faced with the decision of dying as Batman (a fearless martyr, and symbol for good) or living a normal life as Bruce Wayne (a man). His internal conflict is displayed in the crucial shot of his face as he flies across the bay. I wonder: is he actually afraid to die? The old Bruce, I think, would have chosen "to do what others cannot" and overcome the ultimate fear-- death-- and allow the bomb explode with him onboard (similar to the sacrifice he makes at the end of TDK). This is what a "hero" is "supposed" to do, and Nolan actually leads us to believe that he has made this choice. But by ejecting, we see the personal development of Bruce's character. Indeed, Bruce has accepted that he cannot be Batman forever. He is human being, with fears, no different than the rest of us.
EDIT: Wow, I can't believe I actually wrote all that about a comic book movie.
./end rant. They are both still my favorite movies(TDK & TDKR).
lol
