可一而不可再
kě​yī'ér​bù​kě​zài

once is enough

  1. 可 kě auxiliary
    can
    can; may; to be able to; to be permitted to
  2. 一 yī numeral
    one
    one; the number 1; single; alone
  3. 而 ér particleconjunction
    [resultative linker]
    Used in certain constructions to indicate that the second action or state follows immediately from or is the result of the first, as in 一 yī...ér...
  4. 不可 bù​kě auxiliaryadjective
    cannot
    to be unable to; to be impossible
  5. 再 zài
    twice
    (literary) twice; a second time