comedown

arvonalennus A sudden drop to a lower status, condition or level; a disappointment or letdown
1933, (w), (w), Chapter XXVIII, http://www.gutenberg.net.au/ebooks01/0100171h.html

He had two subjects of conversation, the shame and come-down of being a tramp, and the best way of getting a free meal.

“So how are you getting on at UCL?” said Penny kindly, as if it must be a sorry comedown after Oxford.