Re: Stuff you like to believe happened in Nolan's series
I feel his quitting was multi-faceted, personally. It's not just one reason. There's obviously a lot of weight on his mind.
It's not just Rachel, it's not just his not being needed. It's both of those, and more. He became an outcast. He had to have felt horrible about Harvey. The Joker essentially won, and I'm sure that was eating up at him privately.
Why do we fall?