Found online, the "disappointment"-formula on the photo below:
Disappointment (D) equals Expectation (E) divided by Reality (R)
Under this formula, even a realistic expectation results in disappointment: 1E/1R=1D.
That result is true with people that are unthankful. And the eyes of man are never satisfied.
Otherwise, disappointment usually results when expectation > reality.
Even more accurate:
Expectation ≠ Reality = Dissappointment.
In particular on the long term:
(E ≠ R) * Time = Dissappointment.
In the King James bible, you can read:
"For we can do nothing against the truth (...)"
So, wishful thinking doesn't help against reality:
"And whosoever was not found written in the book of life was cast into the lake of fire."
Is your worldview realistic?