half-cocked
adjective /ˌhɑːf ˈkɒkt/
  /ˌhæf ˈkɑːkt/
Idioms Idioms 
go off half-cocked (informal)
- to start before preparations are complete, so that the effect or result is not as it should be没准备好就开始干,操之过急(因而效果或结果不好) - You've got to promise you won't go off half-cocked and do something rash. 你必须保证不会草率行事,做出鲁莽的事情。 
 
- You've got to promise you won't go off half-cocked and do something rash.