Never a big part ? He dedicated completely for that project. That's the only thing we know he did. Its a huge part of his life in that moment. I still dont understand what you disagree , i never said Bruce tried to establish an emotional life , Alfred completely addresses that telling him he didn't even tried.
(also the sleeping is a consequence of him being Batman. Just like the playboy persona. He showed clearly in TDK how to take advantage of his position being Bruce Wayne)
The biggest issue is how Bruce Wayne , "the humanitarian" , also sees himself as a failure.
Exiling himself is the response of a man who cant seem do to anything. As Batman his role became irrelevant. As a philanthropist he didn't achieved his goals. As a simple man , he's not even ready to have a new life . This is the state of Bruce Wayne in the beginning the story , and Rises is nothing but the story of him picking himself up.
(those script passages are crystal clear...but i have already read here that the director didnt understand the movie ...so yeah)