I am with you on that point and makes me wonder too, but i would like to extend it and relate this thing to equilibrium in chemistry Absolute Reality = Distill water 7 Ph
Slightly Positive Reality or Slightly Negative Reality = Drinking water 6.5 to 8.5
Extremists = Pure acid or bases 0 to 14 = Unbearable
Accepting thing as they are is simple because naturally when we were children sad meant crying and good meant laughing and as we grow up and as you mentioned it "positive thinking" movement, it occurred to me that these movements preconditioned some people's minds to think in a way they were not naturally meant to and lie to themselves and every extremism is due to these conditioning of mind which on a small scale we observe around us in relationships and at a larger scale we see as arduous religious followers and fanatics.
RE: Having a Positive Attitude in Life... to Excess?