好自為之

Etymology
Initially from  – see quote below.

Idiom

 * 1)  to like to do everything him/herself in one's own way

Idiom

 * 1)  to do one's best; to endeavour to do something
 * 2)  [You] better behave yourself, otherwise [you] will be in trouble! / You better watch out for yourself! You have been warned!