The phrase "delusional expectation" is correct and usable in written English.
You can use it to refer to an expectation that a person has that is not realistic or likely to happen. Example sentence: His delusional expectation of winning the lottery cost him hundreds of dollars in tickets.
There is the jeweled handbag Condé Nast's wife had engraved with her home address (1040 Park Avenue) in the possibly delusional expectation that it would be returned if ever mislaid.
The word also, not coincidentally, names an emotional disorder described by Freud as "a profoundly painful dejection, cessation of interest in the outside world, loss of the capacity to love, inhibition of all activity, and a lowering of the self-regarding feelings to a degree that finds utterance in self-reproaches and self-revilings, and culminates in a delusional expectation of punishment".
Too miserable to comprehend the present, the characters cling to false memories and delusional expectations.
Many of us arranged our business and personal affairs consistent with these delusional expectations and beliefs.
In his grandiosity, he inflates the facts and figures of his hapless life; and he puffs the same optimistic smoke into his two adult sons, Biff Andrew Garfieldd) and Happy (Finn Wittrock), who bear the scars of his delusional expectations.
The fact is, young girls are bombarded by advertisements and magazines full of delusional expectations that encourage people to like themselves less and then they want to buy more things.
Because you are smarter than most everyone else who lives in a delusional alterniverse of unrealistic expectations and unachievable goals.
He had, after all, been unable to forget the murderous attack and suicide by Gang Lu, a delusional scientist with Einstein-like expectations for his American education.
Don't be the boss whose expectations for neat and orderly change are so delusional that you force your enthusiastic future-thinkers to become hypocrites and package their proposals in slide decks that promise an unrealistic level of certainty.
It's now apparent that such short-term expectations may have been — to use the medical term — delusional.
