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。