...or why the Onion was onto something with the headline "Optimist Half Full of Shit."
There is, of course, a huge gap between "Stay positive so that you don't fall into despair" and "Stay positive, because then the universe will reward you" (which seems an awful lot like a religious argument made by people who would otherwise scoff at the notion of, say, a guardian angel). But still...telling people it's all about attitude is hurtful in two ways. First, it blames people who are powerless to fix their problems (if only you'd wanted it more!). Second, from the other end of things, it perversely encourages inaction (don't try to fix things—just stay happy!).