disillusionment

Etymology

dis- + illusion + -ment

noun

1. A feeling of disappointment, akin to depression, arising from the realization that something is not what it was expected or believed to be, possibly accompanied by philosophical angst from having one's beliefs challenged.
   But till I am thirty, I know that my youth will triumph over everything- every disillusionment, every disgust with life. 1912, Fyodor Dostoevsky, Constance Garnett, “3”, in The Brothers Karamazov, book V
   I catch on your face the old sad smile / Of our ancient disillusionment, / When the ardent crowd tries to beguile / Your world-old soul to impassionment. 1917, John Cowper Powys, “Travellers”, in Mandragora
   They were self-conscious of their disillusionment and demoralization, and their spokesmen—the artists and journalists among them—publicized their cynicism so successfully that it came to be regarded as the mood of a whole decade. October 1940, Mortimer Adler\This Prewar Generation, “Harper's Magazine”, in (Please provide the book title or journal name)
   'Oh, this fair is nothing but a chaos of noise and beggars,' I thought in disillusionment. 'I wonder if Western scientists, patiently enlarging the realms of knowledge for the practical good of mankind, are not more pleasing to God than these idlers who profess religion but concentrate on alms.' 1946, Paramahansa Yogananda, “Chapter 36: Babaji's Interest in the West”, in Autobiography of a Yogi
   1953, Dwight D. Eisenhower, First State of the Union Address, Our country has come through a painful period of trial and disillusionment since the victory of 1945. We anticipated a world of peace and cooperation. The calculated pressures of aggressive communism have forced us, instead, to live in a world of turmoil.
2. The act of freeing from an illusion; the state of being freed therefrom.
   It is a very wholesome and regenerating change which a man undergoes when he "comes to himself." […] It is a process of disillusionment. The scales have fallen away. 1901, Woodrow Wilson, When a Man Comes to Himself, section I