Once you kill a cow, you gotta make a burger by Lady gaga

You know what they say,
"Once you kill a cow, you gotta make a burger"
by Lady gaga

 

It means "Once you decided to do something, you gotta finish it anyway"(Even if the result is different from the original plan)

 

There is a similar proverb in Korea.

 

"Once you take out your sword, at least you gotta cut the radish"

 

When a swordman takes out his sword, usually that is for combat or war.

So it means, Once a swordman takes out his sword, He or she should do use it and not making the sword taking out action in vain.