For a more substantive analysis of how an excess of positivity is causing problems, I highly recommend Byung-Chul Han's book "The Burnout Society". He argues t

For a more substantive analysis of how an excess of positivity is causing problems, I highly recommend Byung-Chul Han's book "The Burnout Society". He argues that Western culture has shifted from a negative "thou shalt not" model to a positive, open-ended "you can" model, and that this is a cause of much of the depression and burnout we see today. And he says that this has happened in capitalist societies because it results in greater efficiency--it gets people to exploit themselves rather than needing to be driven by others.