wow i actually watched this movie like 3 days ago.
Take a look at his abandonment issues and that is why he is creating this fortress around-himself and using his intellect to keep those around him away.
Throughout his entire life he associated change with emotional pain, that is why whenever "change" came in the movie he tended to shy away from it or fight it.
The reason why he never strived to his full potential until he was told "its not your fault". was because he was brought up being punished for the most trivial things and that then gave him the mind se that he was never good enough and that you can't never fail if you don't try.
Throughout his live people have never been able to understand him intellectually so why should they be able to understand him emotionally, but it was when the doctor explained that he had a similar upbringing that Will finally began to tear down the walls that he had spent so many years building up. (you can't get hurt unless you open yourself up to be hurt)
Well those are some just really quick thoughts on what i got from the movie, hope that helps you.