He refused to grow as a person, whether it was conscious, or as I think, unconsciously, he was the same guy she fell in love with, and that didn't work for her anymore, and thats on her too, because she married the guy....but, the dude was a burnout, but a good father...however, as a man, as a husband, he was immature, and too self centered/self involved to notice it in himself. Michelle Williams had probably checked out of the relationships years before the movie takes place, she was over it, she jus didn't know how to end it. Ebert had a great line, regarding the movie, as far as Michelle Williams position, 'He loves me as much as he always did/he loves me the same as he always did....see the difference'? I disagree, Williams was on her way to becoming a doctor, or a promotion, a new job, and Dean was on his way to more 9:00 AM beers, and she realized she hated him for it.