一不做，二不休

yībùzuò,èrbùxiū
  1. lit. either don't do it, or don't rest (idiom)
  2. fig. if you do it at all, you may as well go the whole hog
  3. in for a penny, in for a pound

CEDICT

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 不 bù
  1. no; not so
  2. (bound form) not; un-
3 做 zuò
  1. to make; to produce
  2. to write; to compose
  3. to do; to engage in; to hold (a party etc)
  4. (of a person) to be (an intermediary, a good student etc); to become (husband and wife, friends etc)
  5. (of a thing) to serve as; to be used for
  6. to assume (an air or manner)
4 二 èr
  1. two
  2. 2
  3. (Beijing dialect) stupid
5 不休 bùxiū
  1. endlessly
  2. ceaselessly