Do the thing you fear to do and keep on doing it... that is the quickest and surest way ever yet discovered to conquer fear.
Everything changes as you get older - your mind, your body, the way you view the world.
The great thing about Stephen is that he sees the movie as a separate thing, I think. He wants it to capture the essence of the book, and if he feels that's been done, then he's not too particular about the details. I think that's why he's happy.