Which topic, that the two main characters discuss, has the most influence on Mitch’s character and why?

I think the themes of relationship and attitude are what were most meaningful. Relationships are a big theme in the book. The relationship (past and present) between Morrie and Mitch, between Morrie and his caregivers, between Morrie and his family, and between Mitch and his brother all play a big part in the story. Throughout his illness, Morrie displays a very positive mental attitude. He does not feel sorry for himself because his body is slowly deteriorating. He looks at the positives in his life and the things he is still able to do. His positive attitude inspires Mitch and others in the story.