So, basically I think that the passage from the book is very indicitive of the Christian spiritual journey. You can't just profess Christ as Lord and then do whatever you want because you know you're going to heaven. When we discussed this question in my small group we framed the problem as: "If i'm going to heaven when I die, why the hell should I care about what I do when i'm alive?"
Apologies if anyone is offended, but its true! I admire the Jewish tradition of mitzvot, and feel like Christians are far behind in the whole "actions speak louder than words" thing.