He was prepared!
Its a cliche I don't like but I used it.
There is an interesting dichotomy at work with this film. Fans always say they prefer Batman over actual super powered heroes. Because he is human. But even a man at the height of human physical perfection could never do what Batman does for a long time. While Batman retiring has been criticized, its acknowleding his humanity. Which is a huge part of his appeal.
But another part of his appeal is that he can survive anything. That has been true of most versions of the characters. Even if it pushes the realm of plausibility and this human hero basically is superhuman. Well the movie is being true to the character! I like that for this finale Nolan really embraced the more fantastic comic elements.