The book was so amazing that I read it again and again .He teaches Hazel that every life should be a full life. He believes that everyone should leave a mark on the Earth. Augustus shows her that even if you won't live long, you can live an exciting and complete life. Hazel realizes this near the end of the book, when Gus gets cancer again.John Green has written an incredibly inspiring book, it was inspiring because it showed that even when you know you're dying you still have to make the most of the time you have if you possibly can. That you should always try and live every day to the full. That you should live every day as if it's your last.