I would have to put myself in Michael's shoes if i was in his tragic situation...I would do anything to protect my family, espcially my father if no one else can. Also when Michael was in italy thats where he discovered when Sonny dies and also his new wife was blown up!.. So life pretty much sucks after that. Who wouldn't be depressed after that? So he blocked out all his emotions and became a ruthless business man because everyone he interacts with reminds him of his enimies and actaully become his enimies! Who could blame him?

Michael made all the right choices because he had to and it was his fate!