There are two psychological versions of Batman: Sane and Insane.
In the sane interpretation, Bruce Wayne become Batman because he HAS to. He has no other choice. This is the version that we see in the Dark Knight trilogy. He can't work through the police because they are too corrupt. And works of philanthropy alone cannot save Gotham. Like any sane human being, he doesn't want to keep being Batman forever. He hopes that Harvey Dent can take over for him. He hopes that John Blake can take over for him. He knows that Gotham needs Batman, but he doesn't want the job forever. He has great, sane rationale for dressing up in a Bat costume and taking out thugs.
In the insane interpretation, Bruce Wayne is usually hinted at not being mentally stable. He becomes Batman because he is COMPELLED to. He would kill himself otherwise. This is the version that we see in Batman: Year One (still canon), Batman: Earth One, Michael Keaton's Batman, and Allstar Batman. In Batman: Year One, he nearly kills himself until he gets inspiration from a Bat.
In Batman: Earth One, Bruce doesn't have a reason for dressing like a Bat other than to protect is identity and find his parents killers--there's a real disconnect there. Why didn't he end up like Harvey Bullock or Jim Gordan and try to clean the GCPD from the inside out? Why did he dress like a Bat and take the law into his own hands? He's a little off. He's crazy. His mother is from a long line of people (The Arkhams), who have gone insane.
A lot of writers (Miller, Morrison, Johns, etc.) seem to love telling tales about the insane Batman. But I personally prefer the sane interpretation of the character. Not to bash anyone with mental illness, but having Batman be insane takes away from the character for me. He seems like he's less than us, when he should be the best of us. The story of a normal man training to become a hero because of his sense of responsibility is nullified by the insane interpretation. But that's just my opinion.
Which Batman do you prefer: Sane or Insane?