Originally Posted by Happy Jack
It was about him having a normal life. Rachel was just the gateway that eventually proved to only be illusory. I think there's enough evidence in the films to suggest that if Rachel had lived and Harvey died her relationship with Bruce still would not have worked. Bruce was too wrapped in Batman and his issues even if he didn't realize it. Rachel wasn't his soul mate, that would be Selina Kyle.
The last sentence is also very, very true. Rachel Dawes, if anything, was just a crush, but it's Selina Kyle that is the true love Bruce had been seeking. Selina Kyle understands all that Bruce has gone through.