Complex sentence: Mitch discovers that despite Curly's tough exterior, he is in reality a very wise man, as he gives Mitch advice as how to face his problems: by thinking about just the "one thing" that is most important in his life.
Split into simpler sentences: Mitch discovers that despite Curly's tough exterior, he is a very wise man. Curly advises him how to face his problems: by concentrating on the "one thing" that is most important in his life.