一蹶不振

yījuébùzhèn
  1. one stumble, unable to rise (idiom); a setback leading to total collapse
  2. ruined at a stroke
  3. unable to recover after a minor hitch

CEDICT

  1. (figurative) the subject flipped over after wobbling
  2. one tumbles and unable to speak at all
  3. the subject flipped over after wobbling

Wiktionary

跌了一跤就不敢再走路。語本漢．劉向《說苑．卷一六．談叢》：「一噎之故，絕穀不食；一蹶之故，卻足不行。」後比喻遭受挫折或失敗後，無法再振作恢復。清．王夫之《讀通鑑論．卷四．漢宣帝》：「憚數歲之勞，遽期事之速效，一蹶不振，數十年兵連禍結而不可解。」

重編國語辭典

遭受一次挫折以後就再也振作不起來

維基詞典

Entry Composition

1 一 yī
  1. one
  2. single
  3. a (article)
  4. as soon as
  5. entire; whole; all; throughout
  6. "one" radical in Chinese characters (Kangxi radical 1)
  7. also pr. yāo for greater clarity when spelling out numbers digit by digit
2 蹶 jué
  1. to stumble
  2. to trample
  3. to kick (of horse)
3 不振 bùzhèn
  1. lacking in vitality
  2. depressed (market, spirits etc)