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。语本汉．刘向《说苑．卷一六．谈丛》：「一噎之故，绝穀不食；一蹶之故，却足不行。」后比喻遭受挫折或失败后，无法再振作恢复。清．王夫之《读通鑑论．卷四．汉宣帝》：「惮数岁之劳，遽期事之速效，一蹶不振，数十年兵连祸结而不可解。」

重編國語辭典

遭受一次挫折以后就再也振作不起来

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)