The concept that people need to be grateful for the good things in life has been around probably forever. It’s a form of positivity. Rather than being upset you don’t have the Ferrari the guy next door has, be grateful that you have a Volvo in which to take your kids to school. Seems reasonable enough.
And the movement of gratitude leading to emotional wellness really hit its stride when Oprah started promoting the “gratitude journal”. Basically you write down what you’re grateful for every day and then, “you’ll become a deliberate attractor of positive vibrations”. In Oprah’s case, I’m guessing that’s one really fat journal, and apparently lots of vibrations.