Mark Watney's sense of humor and faith in the whole of humanity, more so than even his scientific MacGyvering, pulls him through events that would leave anyone but him hopeless and heartbroken. The Martian is one of my favorite books, not just because I'm a space nerd, but because of Watney's optimistic outlook and his ability to keep on going despite awful situations - like using your own poop as fertilizer and an endless stream of disco.