In some respects, you do feel badly for Mitty because he hates his life. It is boring and he believes that he is a 'nothing'. However, on the other hand he is failing to see the beauty and joy in his own life. He is so fixated on being someone else that he doesn't stop to figure out who he is or could be. In essence, he's wasting his life away pretending to be something and someone he is not.
